Five batch jobs, A through E$,$ arrive at almost the same time. They have estimated running times of $12,7,1,4$ and $8$ minutes $.$ Their $($externally determined$)$

priorities are $3,5,2,1,$ and $4,$ respectively, with $1$ being the highest priority. For each of the following scheduling algorithms, determine the mean process

turnaround time. Ignore process switching overhead.

a$)$ Round robin.

b$)$ Priority scheduling.

c$)$ First$-$come, first$-$served $($run in order $12,7,1,4,8).$

d$)$ Shortest job first.

For $($a$),$ assume that the system is multiprogrammed, and that each job gets its fair share of the CPU and the time quantum is under a second. For $($b$)$ through

$($d$),$ assume that only one job at a time runs, until it finishes. All jobs are completely CPU bound.