1A. Describe the FOUR events in which CPU-scheduling decisions may take place. Consider the following set of processes, arriving at the given times and having the following CPU burst time and priorities: Process Arrival Burst Time Priority Time(ms) (ms) A 0 8 3 B 3 4 1 5 7 4 D 8 3 2 Draw a Gantt chart and calculate average waiting time and turn-around time of each process using SJF, Priority and Round Robin (quantum 3 ms) CPU scheduling algorithms. Assume pre-emptive scheduling policy for SJF and Priority scheduling. Consider higher the priority value, lower the priority of the process