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Concurrency

Operations

• Balance: Get the balance of an account.

• Deposit: A customer deposits money into one of her accounts, either checking or savings.
  • amount > 0

• Withdrawal: A customer withdraws money from one of his accounts, either checking or savings.
  • amount ≤ balance

• Transfer: A customer transfers money from checking to savings, or in the other direction.
  • 0 < amount ≤ balance of the source account

• Audit: The bank scans all accounts, computing the sum of all balances. (Matched against a record of deposits, withdrawals and transfers — not showing that detail.)

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