Consider the following Java statements, assuming that MyStack is a class that implements the interface StackInterface:

 int n = 4; StackInterface stack = new MyStack<>(); while (n > 0) { stack.push(n); n--; } // end while int result = 1; while (!stack.isEmpty()) { int integer = stack.pop(); result = result * integer; } // end while System.out.println("result = " + result); 

a. What value is displayed when this code executes?

b. What mathematical function does the code evaluate?