System has 5 processors. Time to complete each process i.e. Ti is same.
Reasoning :
T1 executes on Processor 1. other 4 processors are idle.
T2 executes on Processor 1, other 4 Processors are idle.
T3, T4, T5 can run parallely on different different processors. Now 3 processors are working and 2 are still unused.
T6, T7, T8 can run parallely on different different processors. now 3 processors are working and 2 are still idle.
Total 5*4 =40 instance of processors. 8 out of 20 are working.
Efficiency = (8/20)*100 = 40%