Please explain every step

Implement a stack using a single queue. In particular, you are given a queue Q that provides the method Q.size() to return its size at any point and the standard methods of queues (i.e, Q.enqueue(x) and Q.dequeue()). The requirement is to use such methods of Q to implement two methods S.push(x) and S.pop() for a stack S. What are the running times of your methods?