The following is a sequence of stack operations S1.push (12); S1.push (-5); Int t1 = S1.pop(); S1.push (-8); S1.push (20); Int t2 = S1.topValue(); S1.pop (); S1.push (4); I. Assuming all instructions...

The following is a sequence of stack operations
S1.push (12);
S1.push (-5);
Int t1 = S1.pop();
S1.push (-8);
S1.push (20);
Int t2 = S1.topValue();
S1.pop ();
S1.push (4);
I. Assuming all instructions execute in the given sequence, draw four diagrams,

showing the contents of the stack, after executing the second, fourth, sixth,

and eighth instructions. In each diagram, include the values of all elements in

the stack, and a pointer denoting the current "top" of the stack.
II. What are the values of t1 and t2 after the code executes?