Consider the following log sequence of two transactions on a bank account, with initial balance 12000, that transfer 2000 to a mortgage payment and, then apply a 5% interest(i) T1 start(ii) T1 B old = 12000 new = 10000(ii) T1 M old = 0 new = 2000(iv) T1 commit(v) T2 start(vi) T2 B old = 10000 new = 10500(vii) T2 commitSuppose the database system crashed just before log record 7 is written. When the system is restarted, which one statement is true of the recovery procedure?

• A. We must redo log record 6 set B to 10500
• B. We must undo log record 6 to set B to 10000 and then redo log record 2 and 3
• C. We need not redo log records 2 and 3 because transaction T1 has committed
• D. We can apply redo and undo operations in arbitrary order because they are idempotent