Consider two processes, P$1$ and P$2,$ that need to accessa shared resource. To ensure mutual exclusion, a binary semaphoreS is used with an initial value of $1.$ The processes follow the given code structure:

PI

P$2$

wait$($S$)$

Critical Section

signal$($S$)$

wait$($S$)$

Critical Section

signal$($S$)$

a$.$ Explain how the semaphore S ensures mutual exclusion in this scenario.

b$.$ What will happen if the waitS$)$ operation is called when S $=0?$