Consider the following set of processes, with the length of the CPU$-$burst time given

in milliseconds:

The processes are assumed to have arrived in the order $P1,P2,P3,P4,P5,$ all at time $0.$

a$.$ Draw four Gantt charts illustrating the execution of these processes using FCFS$,$ SJF$,$

a non$-$preemptive priority $($a smaller priority number implies a higher priority$),$ and

RR $($quantum $=1)$ scheduling.

b$.$ Which of the schedules in part a result in the minimal average waiting time $($over all

processes$)?$