4. (40 points] Consider a shared variable x, initialized to zero, is operated on by four processes A,B, C, and D. Processes A and B increment x by one while processes C and D decrement x by two. Each process, before reading, performs wait on a semaphore S and signal on S after store. S is initialized with 2 (i.e., S=2). Find what the maximum and minimum values of x are after processes complete execution. Also, show the two sequences (i.e., trace the sequence of interleavings of statements context switches) for getting these maximum and minimum values. Find the visual representation of these four processes in memory below. D A. wait(s) read(x) x++ write(x) signal(x). wait(s) read(x) x++ write(x) signal(x) wait(s) read(x) x++ write(x) signal(x) wait(s) read(x) X++ write(x) signal(x)