Stacks - General Questions

Starting with an empty stack, these operations are performed: push(6), pop(), push(4), pop(), push(1), pop(), push(8). What is at the top of the stack now?

Evaluate the postfix expression: 8 6 * 7 2 * -

Evaluate the postfix expression: 7 5 * 2 1 * -

Starting with an empty stack, these operations are performed: push(7), pop(), push(4), push(4), push(7), push(1), push(7). What is at the top of the stack now?

Evaluate the postfix expression: 8 2 - 4 +