Question 4 1 pts public interface Stack ( Returns the number of elements in the stack. int sizeO 158 * Tests whether the stack is empty. 95/ boolean isEmpty); Inserts an element at the top of the stack. void push(Object e); * Returns, but does not remove, the element at the top of the stack, or null if the stack is empty Object top) * Removes and returns the top element from the stack, or null if the stack is empty. Object pop) Consider the following sequence of operations on a Stack that begins empty. Give the return value for each line. If it causes an error, then write ERROR