diff --git a/training-assignments/src/java/eu/sig/training/ch04-duplication/bankaccounts/CheckingAccount.java b/training-assignments/src/java/eu/sig/training/ch04-duplication/bankaccounts/CheckingAccount.java
index 3e6fdbb..d341c92 100755
--- a/training-assignments/src/java/eu/sig/training/ch04-duplication/bankaccounts/CheckingAccount.java
+++ b/training-assignments/src/java/eu/sig/training/ch04-duplication/bankaccounts/CheckingAccount.java
@@ -1,41 +1,19 @@
-package eu.sig.training.ch04;
+package eu.sig.training.ch04.v3;
+
+import eu.sig.training.ch04.BusinessException;
+import eu.sig.training.ch04.Money;
 
 // tag::CheckingAccount[]
-public class CheckingAccount {
-    private static final float INTEREST_PERCENTAGE = 0.01f;
-    private Money balance = new Money();
+public class CheckingAccount extends Account {
     private int transferLimit = 100;
 
+    @Override
     public Transfer makeTransfer(String counterAccount, Money amount)
         throws BusinessException {
-        // 1. Check withdrawal limit:
         if (amount.greaterThan(this.transferLimit)) {
             throw new BusinessException("Limit exceeded!");
         }
-        // 2. Assuming result is 9-digit bank account number, validate 11-test:
-        int sum = 0;
-        for (int i = 0; i < counterAccount.length(); i++) {
-            char character = counterAccount.charAt(i);
-            int characterValue = Character.getNumericValue(character);
-            sum = sum + (9 - i) * characterValue;
-        }
-        if (sum % 11 == 0) {
-            // 3. Look up counter account and make transfer object:
-            CheckingAccount acct = Accounts.findAcctByNumber(counterAccount);
-            Transfer result = new Transfer(this, acct, amount);
-            return result;
-        } else {
-            throw new BusinessException("Invalid account number!");
-        }
-    }
-
-    public void addInterest() {
-        Money interest = balance.multiply(INTEREST_PERCENTAGE);
-        if (interest.greaterThan(0)) {
-            balance.add(interest);
-        } else {
-            balance.substract(interest);
-        }
+        return super.makeTransfer(counterAccount, amount);
     }
 }
 // end::CheckingAccount[]