(a) A database has eleven transactions running as listed below (the time is shown horizontally from left to right): T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 Time tc tf At time tc a checkpoint is taken, at time #f the database fails due to a power outage. If the database is a write through database, three stages are involved in the recovery process when the database is restarted. Use the diagram above to discuss what happens at each of the three stages and what transactions are involved.