Serial computing. A job J consists of two tasks A and B$.$ Job J completes when its last task completes its execution. Task A with $100$s CPU time $($just as in $2\mathrm{.}2)$ followed by $50$s I$/$O arrives at t$=30$s$,$ the system is empty and A starts execution immediately. Task B with $250$s CPU and $100$s I$/$O arrives at t$=50$s$.$ There is no other program other than A$,$B$.$

a$.$ What is the turnaround time Tr$($A$)$ of task A $?$

b$.$ What is the turnaround time Tr$($B$)$ of task B$?$