John plans to add a new operation Peek to the stackADT. This new operation returns the top element of the stack, but, unlike Pop, the stack is unchanged. The new version of stack.h now looks like the follows. / * File: stack.h */ typedef struct stackCDT *stackADT; typedef int stackElementT; stackADT EmptyStack(void); void Push(stackADT, stackElementT); stackElementT Pop(stackADT); stackElementT Peek(stackADT); / This is new. / int StackDepth(stackADT); int StackIsEmpty(stackADT); John has a new idea of using linked lists to implement the stackADT in the file stack.c. The main ideas are illustrated in the Figure 1. Note: - The type stackADT is, as usual, a pointer to struct stackCDT. typedef struct stackCDT *stackADT; - The structure struct stackCDT contains only one variable named topOfStack, which is a pointer to a structure cellT. If the stack is empty, then topOfStack should be NULL. struct stackCDT { cellT *topOfStack; } - The structure cellT contains two variables: one stackElementT variable named value that stores a stack element, and one pointer named next, which points to the cellT that stores the element below it, or NULL if there is no next element. typedef struct cellT \{ stackElementT value; struct cellT *next; } cellT; John has implemented the Peek operation in stack.c, as follows. stackElementT Peek(stackADT stack) \{ if (StackIsEmpty(stack)) exit(EXIT_FAILURE); \} return stack->topOfStack->value; Implement other parts of the file stack.c using the above ideas