4. (20 points) Consider enqueue(e) and dequeue) methods in queue. Suppose we imple- mented queue interface as we did in class / class lecture notes. The queue is initialized as an empty queue for each of the partial problem. What would be the output for the following sequence of enqueue and dequeue? (a) (5 points) enqueue(2), enqueue(8), enqueue(O), dequeue(), dequeue) (b) (5 points) enqueue(A), enqueue('C"), dequeue(), enqueue('E), dequeue) (c) (5 points) enqueue(acd), enqueue('ak'), dequeue) d (5 points) enqueue(eee'), dequeue(), dequeue)