20. Show what is written by the following segments of code, given that item1, item2, and item3 are int variables, and s is an object that its the abstract description of a stack as given in the section. Assume that you can store and retrieve variables of type int on s.

a.

item1 = 1; item2 = 0; item3 = 4;

s.push(item2); s.push(item1); s.push(item1 + item3);

item2 = s.top();

s.push (item3*item3); s.push(item2); s.push(3);

item1 = s.top();

s.pop();

System.out.println(item1 + " " + item2 + " " + item3);

while (!s.isEmpty())

{

item1 = s.top(); s.pop();

System.out.println(item1);

}

b.

item1 = 4; item3 = 0; item2 = item1 + 1;

s.push(item2); s.push(item2 + 1); s.push(item1);

item2 = s.top(); s.pop();

item1 = item2 + 1;

s.push(item1); s.push(item3);

while (!s.isEmpty())

{

item3 = s.top(); s.pop();

System.out.println(item3);

}

System.out.println(item1 + " " + item2 + " " + item3);