$($a$)$ Four jobs A$,$B$,$C and D arrive at a computer centre at the same time in this sequence. They

have estimated running times of $9,5,3$ and $4$ secs$.$ Their priorities are $3,4,2$ and $1$ respectively,

with $1$ being the highest priority. Find average waiting and average turnaround time using

priority CPU scheduling when there is no preemption. Will the result vary for the given

question if preemption was introduced $?$