Consider the following sequence of two transactions on a bank account (A) with initial balance 20,000 that transfers 5,000 to another account (B) and then apply 10% interest.(i) T1 start(ii) T1 A old = 20,000 new 15,000(iii) T1 B old = 12,000 new = 17,000(iv) T1 commit(v) T2 start(vi) T2 A old = 15,000 new = 16,500(vii) T2 commitSuppose the database system crashes just before log record (vii) is written. When the system is restarted, which one statement is true of the recovery process?

• A. We must redo log record (vi) to set A to 16,500.
• B. We must redo log record (vi) to set A to 16,500 and then redo log records (ii) and (iii).
• C. We need not redo log records (ii) and (iii) because transaction T1 is committed.
• D. We can apply redo and undo operations in arbitrary order because they are idempotent.