3. (12 points) Suppose that the processes arrive in $P_1$, $P_2$, $P_3$, and $P_4$. Run FCFS, SJF preemptive and Round Robin scheduling algorithm. For the Round robin algorithm, Time quantum is set to 1.
Processes Arrival Time Burst Time
$P_1$ 0.0 7
$P_2$ 2.0 4
$P_3$ 4.0 1
$P_4$ 5.0 4
a. Draw Gant Charts for all three algorithms.
b. Compute average waiting time for three algorithms.
c. Which algorithms is the best in terms of average waiting time?