diff --git a/abcbank/account.py b/abcbank/account.py
index e010009..5fcff40 100644
--- a/abcbank/account.py
+++ b/abcbank/account.py
@@ -1,4 +1,5 @@
-from abcbank.transaction import Transaction
+from transaction import Transaction
+from date_provider import DateProvider
 
 CHECKING = 0
 SAVINGS = 1
@@ -20,24 +21,31 @@ def withdraw(self, amount):
         if (amount <= 0):
             raise ValueError("amount must be greater than zero")
         else:
-            self.transactions.append(Transaction(-amount))
+            if self.sumTransactions() >= amount:
+                self.transactions.append(Transaction(-amount))
+            else:
+                raise ValueError("Not sufficient amount in the account to withdraw")
 
     def interestEarned(self):
-        amount = self.sumTransactions()
+        days_in_year = 365
+        actual_amount = self.sumTransactions()
+        amount = actual_amount
         if self.accountType == SAVINGS:
-            if (amount <= 1000):
-                return amount * 0.001
-            else:
-                return 1 + (amount - 1000) * 0.002
+            for day in range((self.transactions[-1].transactionDate - self.transactions[0].transactionDate).days):
+                if amount <= 1000:
+                    amount += amount * 0.001/days_in_year
+                else:
+                    amount += 1 + (amount - 1000) * 0.002/days_in_year
         if self.accountType == MAXI_SAVINGS:
-            if (amount <= 1000):
-                return amount * 0.02
-            elif (amount <= 2000):
-                return 20 + (amount - 1000) * 0.05
-            else:
-                return 70 + (amount - 2000) * 0.1
+            for each_transaction in self.transactions:
+                if (DateProvider.now() - each_transaction.transactionDate).days <= 10:
+                    amount += amount * 0.001/days_in_year
+                else:
+                    amount += amount * 0.05/days_in_year
         else:
-            return amount * 0.001
+            for day in range((self.transactions[-1].transactionDate - self.transactions[0].transactionDate).days):
+                amount += amount * 0.001/days_in_year
+        return amount - actual_amount
 
     def sumTransactions(self, checkAllTransactions=True):
-        return sum([t.amount for t in self.transactions])
\ No newline at end of file
+        return sum([t.amount for t in self.transactions])
diff --git a/abcbank/bank.py b/abcbank/bank.py
index 44711fe..ec7185a 100644
--- a/abcbank/bank.py
+++ b/abcbank/bank.py
@@ -18,7 +18,6 @@ def totalInterestPaid(self):
         return total
     def getFirstCustomer(self):
         try:
-            self.customers = None
             return self.customers[0].name
         except Exception as e:
             print(e)
diff --git a/abcbank/customer.py b/abcbank/customer.py
index 7cfd62a..e56be31 100644
--- a/abcbank/customer.py
+++ b/abcbank/customer.py
@@ -50,6 +50,22 @@ def withdrawalOrDepositText(self, transaction):
         else:
             return "N/A"
 
+    def transfer(self, from_acc, to_acc, transfer_amount):
+        result = False
+        try:
+            if len(self.accounts) > 1:
+                if from_acc.sumTransactions() >= transfer_amount:
+                    from_acc.withdraw(transfer_amount)
+                    to_acc.deposit(transfer_amount)
+                    result = True
+                else:
+                    raise ValueError("Amount in the from account is not sufficient")
+            else:
+                raise ValueError("More than one account needed for transfer")
+        except Exception as error:
+            print "ERROR : " + str(error)
+        return result
+
 
 def _toDollars(number):
     return "${:1.2f}".format(number)
diff --git a/tests/bank_tests.py b/tests/bank_tests.py
index 6de98db..4b51a14 100644
--- a/tests/bank_tests.py
+++ b/tests/bank_tests.py
@@ -1,10 +1,8 @@
 from nose.tools import assert_equals
-
 from account import Account, CHECKING, MAXI_SAVINGS, SAVINGS
 from bank import Bank
 from customer import Customer
 
-
 def test_customer_summary():
     bank = Bank()
     john = Customer("John").openAccount(Account(CHECKING))
diff --git a/tests/customer_tests.py b/tests/customer_tests.py
index 0211a4f..fc61d4d 100644
--- a/tests/customer_tests.py
+++ b/tests/customer_tests.py
@@ -1,5 +1,5 @@
-from nose.tools import assert_equals, nottest
-
+from nose.tools import assert_equals, nottest, raises
+from bank import Bank
 from account import Account, CHECKING, SAVINGS
 from customer import Customer
 
@@ -33,4 +33,43 @@ def test_twoAccounts():
 def test_threeAccounts():
     oscar = Customer("Oscar").openAccount(Account(SAVINGS))
     oscar.openAccount(Account(CHECKING))
-    assert_equals(oscar.numAccs(), 3)
\ No newline at end of file
+    assert_equals(oscar.numAccs(), 3)
+
+bank = Bank()
+checkingAccount = Account(CHECKING)
+savingAccount = Account(SAVINGS)
+bill = Customer("Bill")
+bill.openAccount(checkingAccount)
+bill.openAccount(savingAccount)
+bank.addCustomer(bill)
+checkingAccount.deposit(100.0)
+checkingAccount.deposit(500.0)
+checkingAccount.deposit(2000.0)
+savingAccount.deposit(900.0)
+
+from_acc = checkingAccount
+to_acc = savingAccount
+
+def test_transfer_success():
+    transfer_amount = 100
+    result = bill.transfer(from_acc, to_acc, transfer_amount)
+    assert_equals(result, True)
+    assert_equals(checkingAccount.sumTransactions(), 2500.0)
+    assert_equals(savingAccount.sumTransactions(), 1000.0)
+
+@raises(ValueError)
+def test_transfer_insufficient_balance_failure():
+    transfer_amount = 5000
+    result = bill.transfer(from_acc, to_acc, transfer_amount)
+
+@raises(ValueError)
+def test_transfer_insufficient_balance_failure():
+    checkingAccount_oscar = Account(CHECKING)
+    oscar = Customer("Oscar").openAccount(checkingAccount_oscar)
+    bank.addCustomer(oscar)
+    checkingAccount_oscar.deposit(100.0)
+    transfer_amount = 5000
+    from_acc = checkingAccount_oscar
+    to_acc = savingAccount
+    result = bill.transfer(from_acc, to_acc, transfer_amount)
+