diff --git a/src/main/scala/com/abc/Account.scala b/src/main/scala/com/abc/Account.scala
index fa23d85..359a6f5 100644
--- a/src/main/scala/com/abc/Account.scala
+++ b/src/main/scala/com/abc/Account.scala
@@ -1,44 +1,74 @@
 package com.abc
 
 import scala.collection.mutable.ListBuffer
+import java.util.Calendar
+import java.util.Date
 
-object Account {
-  final val CHECKING: Int = 0
-  final val SAVINGS: Int = 1
-  final val MAXI_SAVINGS: Int = 2
-}
-
-class Account(val accountType: Int, var transactions: ListBuffer[Transaction] = ListBuffer()) {
+abstract class Account(val transactions: ListBuffer[Transaction] = ListBuffer()) {
 
   def deposit(amount: Double) {
     if (amount <= 0)
       throw new IllegalArgumentException("amount must be greater than zero")
     else
-      transactions += Transaction(amount)
+      transactions += new RealTransaction(amount)
   }
 
   def withdraw(amount: Double) {
     if (amount <= 0)
       throw new IllegalArgumentException("amount must be greater than zero")
     else
-      transactions += Transaction(-amount)
+      transactions += new RealTransaction(-amount)
   }
 
   def interestEarned: Double = {
-    val amount: Double = sumTransactions()
-    accountType match {
-      case Account.SAVINGS =>
-        if (amount <= 1000) amount * 0.001
-        else 1 + (amount - 1000) * 0.002
-      case Account.MAXI_SAVINGS =>
-        if (amount <= 1000) return amount * 0.02
-        if (amount <= 2000) return 20 + (amount - 1000) * 0.05
-        70 + (amount - 2000) * 0.1
-      case _ =>
-        amount * 0.001
-    }
+    val amount: Double = sumTransactions
+    calculateInterest(amount)
+  }
+
+  def addTransaction(t: Transaction): Unit = transactions += t
+
+  def sumTransactions: Double = transactions.map(_.amount).sum
+
+  protected def calculateInterest(amount: Double): Double
+
+}
+
+case class CheckingAccount(override val transactions: ListBuffer[Transaction] = ListBuffer()) extends Account(transactions) {
+  def calculateInterest(amount: Double) = amount * 0.001
+  override def toString = "Checking Account"
+}
+
+case class SavingsAccount(override val transactions: ListBuffer[Transaction] = ListBuffer()) extends Account(transactions) {
+  def calculateInterest(amount: Double) = {
+    if (amount <= 1000) amount * 0.001
+    else 1 + (amount - 1000) * 0.002
   }
+  override def toString = "Savings Account"
+}
 
-  def sumTransactions(checkAllTransactions: Boolean = true): Double = transactions.map(_.amount).sum
+case class MaxiSavingsAccount(override val transactions: ListBuffer[Transaction] = ListBuffer()) extends Account(transactions) {
+  def calculateInterest(amount: Double) = {
+    /**
+    if (amount <= 1000) amount * 0.02
+    else if (amount <= 2000) 20 + (amount - 1000) * 0.05
+    else 70 + (amount - 2000) * 0.1
+    */
+    if ( hasWithdrawalInPastTenDays )
+      amount * 0.001
+    else
+      amount * 0.05
+  }
 
+  override def toString = "Maxi Savings Account"
+
+  def hasWithdrawalInPastTenDays: Boolean = {
+    val now = DateProvider.now
+
+    val cal = Calendar.getInstance()
+    cal.setTime(now)
+    cal.add(Calendar.DATE, -10)
+    val tenDaysAgo = cal.getTime
+
+    transactions.exists( t => t.transactionDate.after(tenDaysAgo) && t.amount < 0.0 )
+  }
 }
\ No newline at end of file
diff --git a/src/main/scala/com/abc/Bank.scala b/src/main/scala/com/abc/Bank.scala
index 4667c0e..a534644 100644
--- a/src/main/scala/com/abc/Bank.scala
+++ b/src/main/scala/com/abc/Bank.scala
@@ -23,22 +23,15 @@ class Bank {
   def totalInterestPaid: Double = {
     var total: Double = 0
     for (c <- customers) total += c.totalInterestEarned
-    return total
+    total
   }
 
   def getFirstCustomer: String = {
-    try {
-      customers = null
-      customers(0).name
-    }
-    catch {
-      case e: Exception => {
-        e.printStackTrace
-        return "Error"
-      }
-    }
+    if(customers.nonEmpty )
+      customers.head.name
+    else
+      "Error"
   }
-
 }
 
 
diff --git a/src/main/scala/com/abc/Customer.scala b/src/main/scala/com/abc/Customer.scala
index 6c517b0..fdeed76 100644
--- a/src/main/scala/com/abc/Customer.scala
+++ b/src/main/scala/com/abc/Customer.scala
@@ -20,7 +20,7 @@ class Customer(val name: String, var accounts: ListBuffer[Account] = ListBuffer(
     //JIRA-123 Change by Joe Bloggs 29/7/1988 start
     var statement: String = null //reset statement to null here
     //JIRA-123 Change by Joe Bloggs 29/7/1988 end
-    val totalAcrossAllAccounts = accounts.map(_.sumTransactions()).sum
+    val totalAcrossAllAccounts = accounts.map(_.sumTransactions).sum
     statement = f"Statement for $name\n" +
       accounts.map(statementForAccount).mkString("\n", "\n\n", "\n") +
       s"\nTotal In All Accounts ${toDollars(totalAcrossAllAccounts)}"
@@ -28,14 +28,8 @@ class Customer(val name: String, var accounts: ListBuffer[Account] = ListBuffer(
   }
 
   private def statementForAccount(a: Account): String = {
-    val accountType = a.accountType match {
-      case Account.CHECKING =>
-        "Checking Account\n"
-      case Account.SAVINGS =>
-        "Savings Account\n"
-      case Account.MAXI_SAVINGS =>
-        "Maxi Savings Account\n"
-    }
+    val accountType = a.toString + "\n"
+
     val transactionSummary = a.transactions.map(t => withdrawalOrDepositText(t) + " " + toDollars(t.amount.abs))
       .mkString("  ", "\n  ", "\n")
     val totalSummary = s"Total ${toDollars(a.transactions.map(_.amount).sum)}"
@@ -50,5 +44,16 @@ class Customer(val name: String, var accounts: ListBuffer[Account] = ListBuffer(
     }
 
   private def toDollars(number: Double): String = f"$$$number%.2f"
+
+  def transfer(fromAccount: Account, toAccount:Account, amount: Double) = {
+    if( ! accounts.contains(fromAccount) || ! accounts.contains(toAccount) ) {
+      throw new IllegalArgumentException("cannot tranfers between accounts not owned")
+    }
+    if( amount <= 0.0 ) {
+      throw new IllegalArgumentException("transfer amount must be greater than zero")
+    }
+    fromAccount.withdraw(amount)
+    toAccount.deposit(amount)
+  }
 }
 
diff --git a/src/main/scala/com/abc/DateProvider.scala b/src/main/scala/com/abc/DateProvider.scala
index c43f6e1..11792bc 100644
--- a/src/main/scala/com/abc/DateProvider.scala
+++ b/src/main/scala/com/abc/DateProvider.scala
@@ -4,17 +4,10 @@ import java.util.Calendar
 import java.util.Date
 
 object DateProvider {
-  def getInstance: DateProvider = {
-    if (instance == null) instance = new DateProvider
-    instance
-  }
-
-  private var instance: DateProvider = null
-}
 
-class DateProvider {
   def now: Date = {
-    return Calendar.getInstance.getTime
+    Calendar.getInstance.getTime
   }
 }
 
+
diff --git a/src/main/scala/com/abc/Transaction.scala b/src/main/scala/com/abc/Transaction.scala
index ba6cec8..8421915 100644
--- a/src/main/scala/com/abc/Transaction.scala
+++ b/src/main/scala/com/abc/Transaction.scala
@@ -1,6 +1,15 @@
 package com.abc
 
-case class Transaction(var amount: Double) {
-  val transactionDate = DateProvider.getInstance.now
+import java.util.Date
+
+trait Transaction {
+  def amount: Double
+  def transactionDate: Date
+}
+
+case class RealTransaction(var amount: Double) extends Transaction {
+  def transactionDate = DateProvider.now
 }
 
+case class FakeTransaction(var amount: Double, var transactionDate: Date) extends Transaction
+
diff --git a/src/test/scala/com/abc/BankTest.scala b/src/test/scala/com/abc/BankTest.scala
index 13b3067..f835481 100644
--- a/src/test/scala/com/abc/BankTest.scala
+++ b/src/test/scala/com/abc/BankTest.scala
@@ -1,19 +1,36 @@
 package com.abc
 
 import org.scalatest.{Matchers, FlatSpec}
+import java.util.Date
+import java.util.Calendar
 
 class BankTest extends FlatSpec with Matchers {
 
   "Bank" should "customer summary" in {
     val bank: Bank = new Bank
-    var john: Customer = new Customer("John").openAccount(new Account(Account.CHECKING))
+    val john: Customer = new Customer("John").openAccount(new CheckingAccount())
     bank.addCustomer(john)
     bank.customerSummary should be("Customer Summary\n - John (1 account)")
+    john.openAccount(new SavingsAccount())
+    val jane: Customer = new Customer("Jane").openAccount(new MaxiSavingsAccount())
+    bank.addCustomer(jane)
+    bank.customerSummary should be("Customer Summary\n - John (2 accounts)\n - Jane (1 account)")
+  }
+
+  it should "first customer" in {
+    val bank: Bank = new Bank
+    bank.getFirstCustomer should be("Error")
+
+    val john: Customer = new Customer("John").openAccount(new CheckingAccount())
+    bank.addCustomer(john)
+    val jane: Customer = new Customer("Jane").openAccount(new MaxiSavingsAccount())
+    bank.addCustomer(jane)
+    bank.getFirstCustomer should be("John")
   }
 
   it should "checking account" in {
     val bank: Bank = new Bank
-    val checkingAccount: Account = new Account(Account.CHECKING)
+    val checkingAccount: Account = new CheckingAccount()
     val bill: Customer = new Customer("Bill").openAccount(checkingAccount)
     bank.addCustomer(bill)
     checkingAccount.deposit(100.0)
@@ -22,18 +39,55 @@ class BankTest extends FlatSpec with Matchers {
 
   it should "savings account" in {
     val bank: Bank = new Bank
-    val checkingAccount: Account = new Account(Account.SAVINGS)
-    bank.addCustomer(new Customer("Bill").openAccount(checkingAccount))
-    checkingAccount.deposit(1500.0)
+    val savingsAccount: Account = new SavingsAccount()
+    bank.addCustomer(new Customer("Bill").openAccount(savingsAccount))
+    savingsAccount.deposit(1500.0)
     bank.totalInterestPaid should be(2.0)
+    savingsAccount.withdraw(700)
+    bank.totalInterestPaid should be(0.8)
   }
 
   it should "maxi savings account" in {
     val bank: Bank = new Bank
-    val checkingAccount: Account = new Account(Account.MAXI_SAVINGS)
-    bank.addCustomer(new Customer("Bill").openAccount(checkingAccount))
+    val maxiSavingsAccount: Account = new MaxiSavingsAccount()
+    bank.addCustomer(new Customer("Bill").openAccount(maxiSavingsAccount))
+    /**
     checkingAccount.deposit(3000.0)
     bank.totalInterestPaid should be(170.0)
+    checkingAccount.withdraw(1200.0)
+    bank.totalInterestPaid should be(60.0)
+    checkingAccount.withdraw(1200.0)
+    bank.totalInterestPaid should be(12.0)
+      */
+    val now:Date  = DateProvider.now
+    maxiSavingsAccount.addTransaction(new FakeTransaction(1000, now))
+    bank.totalInterestPaid should be(50)
+
+    val cal = Calendar.getInstance()
+    cal.setTime(now)
+    cal.add(Calendar.DATE, -11)
+    val elevenDaysAgo = cal.getTime
+
+    maxiSavingsAccount.addTransaction(new FakeTransaction(-200, elevenDaysAgo))
+    bank.totalInterestPaid should be(40)
+
+    cal.add(Calendar.DATE, 3)
+    val eightDaysAgo = cal.getTime
+
+    maxiSavingsAccount.addTransaction(new FakeTransaction(-200, eightDaysAgo))
+
+    bank.totalInterestPaid should be(0.6)
   }
 
+  it should "total interest" in {
+    val bank: Bank = new Bank
+    val checkingAccount: Account = new CheckingAccount()
+    val bill: Customer = new Customer("Bill").openAccount(checkingAccount)
+    bank.addCustomer(bill)
+    checkingAccount.deposit(100.0)
+    val savingsAccount: Account = new SavingsAccount()
+    bank.addCustomer(new Customer("Carol").openAccount(savingsAccount))
+    savingsAccount.deposit(1500.0)
+    bank.totalInterestPaid should be(2.1)
+  }
 }
diff --git a/src/test/scala/com/abc/CustomerTest.scala b/src/test/scala/com/abc/CustomerTest.scala
index 96652b4..c455768 100644
--- a/src/test/scala/com/abc/CustomerTest.scala
+++ b/src/test/scala/com/abc/CustomerTest.scala
@@ -4,8 +4,8 @@ import org.scalatest.{Matchers, FlatSpec}
 
 class CustomerTest extends FlatSpec with Matchers {
   "Customer" should "statement" in {
-    val checkingAccount: Account = new Account(Account.CHECKING)
-    val savingsAccount: Account = new Account(Account.SAVINGS)
+    val checkingAccount: Account = new CheckingAccount()
+    val savingsAccount: Account = new SavingsAccount()
     val henry: Customer = new Customer("Henry").openAccount(checkingAccount).openAccount(savingsAccount)
     checkingAccount.deposit(100.0)
     savingsAccount.deposit(4000.0)
@@ -17,19 +17,40 @@ class CustomerTest extends FlatSpec with Matchers {
   }
 
   it should "testOneAccount" in {
-    val oscar: Customer = new Customer("Oscar").openAccount(new Account(Account.SAVINGS))
+    val oscar: Customer = new Customer("Oscar").openAccount(new SavingsAccount())
     oscar.numberOfAccounts should be(1)
-  }
 
-  it should "testTwoAccount" in {
-    val oscar: Customer = new Customer("Oscar").openAccount(new Account(Account.SAVINGS))
-    oscar.openAccount(new Account(Account.CHECKING))
+    oscar.openAccount(new CheckingAccount())
     oscar.numberOfAccounts should be(2)
   }
 
-  ignore should "testThreeAcounts" in {
-    val oscar: Customer = new Customer("Oscar").openAccount(new Account(Account.SAVINGS))
-    oscar.openAccount(new Account(Account.CHECKING))
-    oscar.numberOfAccounts should be(3)
+  it should "throw IllegalArgumentException for negative withdrawal/deposit" in {
+    val checkingAccount: Account = new CheckingAccount()
+    a [IllegalArgumentException] should be thrownBy {
+      checkingAccount.withdraw(-1000)
+    }
+    a [IllegalArgumentException] should be thrownBy {
+      checkingAccount.deposit(-1000)
+    }
   }
+
+  it should "transfer" in {
+    val checkingAccount: Account = new CheckingAccount()
+    checkingAccount.deposit(1000.0)
+    val savingsAccount: Account = new SavingsAccount()
+    savingsAccount.deposit(200.0)
+    val henry: Customer = new Customer("Henry")
+
+    a [IllegalArgumentException] should be thrownBy {
+      henry.transfer(checkingAccount, savingsAccount, 500.0)
+    }
+
+    henry.openAccount(checkingAccount)
+    henry.openAccount(savingsAccount)
+    henry.transfer(checkingAccount, savingsAccount, 500.0)
+
+    checkingAccount.sumTransactions should be(500.0)
+    savingsAccount.sumTransactions should be (700.0)
+  }
+
 }
diff --git a/src/test/scala/com/abc/TransactionTest.scala b/src/test/scala/com/abc/TransactionTest.scala
index cb24c59..b9c0b28 100644
--- a/src/test/scala/com/abc/TransactionTest.scala
+++ b/src/test/scala/com/abc/TransactionTest.scala
@@ -4,7 +4,7 @@ import org.scalatest.{FlatSpec, Matchers}
 
 class TransactionTest extends FlatSpec with Matchers {
   "Transaction" should "type" in {
-    val t = new Transaction(5)
+    val t = new RealTransaction(5)
     t.isInstanceOf[Transaction] should be(true)
   }
 }