Problem 1. Describe the output of each pop () operation in the following sequence of operations on an initially empty stack: push(56),push(6),push(83),pop(),push(15),pop(),pop(). Problem 2. Describe the output of each de-queue() operation in the following sequence of operations on an initially empty stack: en-queue (56), en-queue(6), en-queue(83), de-queue () , en-queue (15), de-queue () , de-queue ()