21. Suppose three concurrent processes execute the following code:

Explain how the code guarantees mutual exclusion of all three critical sections.

Process P1 do wait (mutEx); critical section signal (mut Ex); remainder section while (!donel); Process P2 do wait (mutEx); critical section signal (mut Ex); remainder section while (!done2); Process P3 do wait (mutEx); critical section signal (mutEx); remainder section while (!done3);