Assume there is a shared variable x, initialized to 0, that is operated on by four concurrently executing processes (A, B, C, and D) as shown below: Process A Process B Process C Process D
semWait(s); semWait(s); semWait(s); semWait(s);
read(x); read(x); read(x); read(x);
x = x - 2; x = x - 3; x = x + 2; x = x + 3;
write(x); write(x); write(x); write(x);
semSignal(s); semSignal(s); semSignal(s); semSignal(s);

Note that each process, before reading x, invokes the semWait operation on a counting semaphore s and invokes the semSignal operation on the semaphore s after writing x. The counting semaphore s is initialized to a value of 2. The processes can arrive in any order and can be preempted at any point in their execution by another process. Answer the following questions:

a. What is the maximum possible value of x after all 4 processes complete execution? Show how this value would be achieved and the order of execution necessary for this to occur.
b. What is the minimum possible value of x after all 4 processes complete execution? Show how this value would be achieved and the order of execution necessary for this to occur.