$5-6$ Short Answer: Bags, Stacks and Queues $[8$ points$]4.$ Trace a stack $($called S$)$ through the following operations:

Stack S $=$ new Stack$()$; S$.$push$($new Integer$(2))$;

S$.$push$($new Integer$(7))$;

Integer X $=$ S$.$pop$()$; S$.$push$($new Integer$(8))$; S$.$push$($new Integer$(5))$;

Integer X $=$ S$.$pop$()$; Integer Y $=$ S$.$peek$()$;

S$.$push$($new Integer$(3))$; Integer Z $=$ S$.$pop$()$;

$($a$)$ Give the contents of the stack after this code has been executed. Indicate the elements in order and label the top. $[2$ points$]$

$2$

$($b$)$ Give the contents of the stack after this code has been executed. Indicate the elements in order and label the top. $[2$ points$]$

$5.$ Trace a queue $($called Q$)$ through the following operations:

Queue Q $=$ new Queue $()$; Q$.$enqueue$($new Integer$(3))$;

Integer X $=$ Q$.$dequeue$()$; Q$.$enqueue$($new Integer$(12))$; Q$.$enqueue$($new Integer$(5))$; Q$.$enqueue$($new Integer$(1))$;

Integer Y $=$ Q$.$ first $()$; Q$.$enqueue$($new Integer$(9))$;

Integer Z $=$ Q$.$dequeue$()$;

$($a$)$ What is the value of Y after it has been assigned? $[2$ points$]$

$($b$)$ Give the contents of the queue after the code has been executed. Indicate the elements in order and label the front. $[2$ points$]$