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+# Bank Account
+
+You are given a simplified multi-threaded “bank account” implementation used by one of our infrastructure teams. The current code processes deposits concurrently but produces incorrect results.
+
+```
+class BankAccount:
+    def __init__(self, balance):
+        self.balance = balance
+
+    def deposit(self, amount):
+        new_balance = self.balance + amount  # read
+        time.sleep(0.1)                      # simulate delay
+        self.balance = new_balance           # write
+
+account = BankAccount(0)
+
+with ThreadPoolExecutor(max_workers=2) as executor:
+    futures = [
+        executor.submit(account.deposit, 500),
+        executor.submit(account.deposit, 700),
+    ]
+```
+
+Task
+
+Identify the concurrency bugs in the implementation.
+
+Explain why these bugs occur.
+
+Fix the implementation without modifying the existing BankAccount class directly.
+
+You may use subclassing (Python) or embedding (Go-style composition), depending on the language you choose.
+
+Ensure your solution is thread-safe and produces the correct final balance (1200).