$A=1,B=0$
$P_{1}$ |
$P_{2}$ |
$P(B)$ |
$P(A)$ |
$R_{1}$ |
$R_{1}$ |
$R_{2}$ |
$V(B)$ |
$V(A)$ |
$P(A)$ |
$P(B)$ |
$R_{2}$ |
$R_{3}$ |
$R_{3}$ |
$R_{4}$ |
$V(B)$ |
$V(A)$ |
$P(A)$ |
|
$R_{4}$ |
This satisfies all the given conditions. So, $2$ binary semaphores are required.
Correct me if I'm wrong