VAs the vertical lines in the chart above indicate, checkpoints are taken at time points t $=0,$ t $=5,$ t $=10,$ t $=15,$ t $=20,$ t $=25,$ etc. To support transaction recovery, two lists of transactions $($UNDO and REDO$)$ are maintained. This question applies to these lists at time points t $=15$ and t $=20.$ Complete the table below by:

Writing UNDO if the corresponding transaction is in the UNDO list at the given time.

Writing REDO if the corresponding transaction is in the REDO list at the given time.

Writing X if the corresponding transaction is in neither of the two lists at the given time.

Transaction

t $=5$

t $=10$

t $=15$

t $=20$

T$1$

Blank $1$

Blank $2$

Blank $3$

Blank $4$

T$2$

Blank $5$

Blank $6$

Blank $7$

Blank $8$

T$3$

Blank $9$

Blank $10$

Blank $11$

Blank $12$

T$4$

Blank $13$

Blank $14$

Blank $15$

Blank $16$

T$5$

Blank $17$

Blank $18$

Blank $19$

Blank $20$

T$6$

Blank $21$

Blank $22$

Blank $23$

Blank $24$

T$7$

Blank $25$

Blank $26$

Blank $27$

Blank $28$

T$8$

Blank $29$

Blank $30$

Blank $31$

Blank $32$

T$9$

Blank $33$

Blank $34$

Blank $35$

Blank $36$

T$10$

Blank $37$

Blank $38$

Blank $39$

Blank $40$

Blank $1.................$

Blank $2.................$

Blank $3.................$

Blank $4.................$

Blank $5.................$

Blank $6.................$

Blank $7.................$

Blank $8.................$

Blank $9.................$

Blank $10.................$

Blank $11.................$

Blank $12.................$

Blank $13.................$

Blank $14.................$

Blank $15.................$

Blank $16.................$

Blank $17.................$

Blank $18.................$

Blank $19.................$

Blank $20.................$

Blank $21.................$

Blank $22.................$

Blank $23.................$

Blank $24.................$

Blank $25.................$

Blank $26.................$

Blank $27.................$

Blank $28.................$

Blank $29.................$

Blank $30.................$

Blank $31.................$

Blank $32.................$

Blank $33.................$

Blank $34.................$

Blank $35.................$

Blank $36.................$

Blank $37.................$

Blank $38.................$

Blank $39.................$

Blank $40.................$