Consider a queue between the two processes indicated below. N is the capacity (maximum length) of the queue; e, f, and b are semaphores. "P" refers to the operation of acquiring (decrementing) a semaphore, and "V" refers to the operation of releasing (incrementing) a semaphore. init() { e = N; f = 0; b = 1; queue = EMPTY; } process1() { for(;;) { P(e); P(b); queue.enqueue(...); V(b); V(f); } } process2() { for(;;) { P(f); P(b); ... = queue.dequeue(); V(b); V(e); } } Which of the following statements is (are) true? (Zero or more may be correct.) a. The purpose of semaphore f is to ensure that dequeue is not executed on an empty queue. b. The purpose of semaphore e is to ensure that deadlock does not occur. c. The purpose of semaphore b is to provide mutual exclusion for queue operations. d. None of the above.

If V is a vector with n items and subroutine Exchange swaps its arguments, then the following code fragment sorts V in descending order. for( j = 0; j < n - 1; j++ ) for( k = 0; k < n - j - 1; k++ ) if( V[k] < V[k+1] ) Exchange( V[k], V[k+1] ); How many calls to Exchange are made if initially, V[i]=i, for i = 0, 1, 2, ..., n - 1 ? a. n-1 b. n c. n(n-1)/2 d. (n-1)(n-2) e. n(n-1)