hello friends i am having doubt in a question that i read in GKP book. Here's the question

Consider a set of 5 processes whose arrivel time,CPU time needed and priority are given below:
Process priority Arrivel time(ms) CPU time needed pririority
P1 0 10 5
P2 0 3 1
P3 2 3 1
P4 5 20 4
P5 10 2 3

smaller the number , higher the priority

question : if CPU scheduling policy FCFS,the average waiting time will be ?

1. 12.8 ms
2. 8 ms
3. 6ms

Thanks in advance 😀