Q63

The $P$ and $V$ operations on counting semaphores, where s is a counting semaphore, are defined as follows: $P(s):$ $s=s-1;$ If $s < 0$ then wait; $V(s):$ $s=s+1;$ If $s \leq0$ then wake up process waiting on s; Assume that $P_b$ and $V_b$ the wait and signal operations on binary semaphores are provided. Two binary semaphores $x_b$ and $y_b$ are used to implement the semaphore operations $P(s)$ and $V(s)$ as follows: $P(s):$ $\quad P_b(x_b);$ $\quad s = s-1;$ $\quad \text{if } (s<0)$ $\quad \{$ $\qquad V_b(x_b);$ $\qquad P_b(y_b);$ $\quad \}$ $\quad \text{ else } V_b(x_b);$ $V(s):$ $\quad P_b(x_b);$ $\quad s= s+1;$ $\quad \text{if } (s\leq0) V_b(y_b) ;$ $\quad V_b(x_b);$ The initial values of $x_b$ and $y_b$ are respectively