We are using undo/redo logging to recover the database after a system crash. The log on the disk looks like the followino. How to recover the database (do you redo, undo, or ignore T1,T2,T3, and T4) ? and what are the values of A,B,C, and D before and after the recovery (if the value is unsure, type "unknown")? Please fill the two tables below. Transaction Recover Plan (redo, undo, or ignore) Value Value before Recovery Value after Recovery A B C