20. Stack operations are

• Push(item): S.push(item) pushes item into the stack S.
• Pop(): S.Pop() removes top of the stack S.
• isEmpty(): S.isEmpty() answers whether the stack S is empty.

The questions are about implementing a FIFO queue Q by using two stacks S1 and S2.

(a) (2%). Describe the algorithm enQueue(item) (insert item into Q) using pseudo code.

(b) (2%). Describe the algorithm deQueue() (delete an item from the Q) using pseudo code.

(c) (4%). Show that deQueue takes O(1) amortized cost.