Stacks - General Questions

Starting with an empty stack, these operations are performed: push(5), push(2), push(6), push(8), pop(), pop(), push(3). What is at the top of the stack now?

Starting with an empty stack, these operations are performed: push(9), pop(), push(7), pop(), push(8), push(8), pop(). What is at the top of the stack now?

Convert the infix expression (A+B*C)*D to postfix.

Starting with an empty stack, these operations are performed: push(6), push(8), push(7), push(1), push(5), pop(), pop(). What is at the top of the stack now?

Starting with an empty stack, these operations are performed: push(5), push(7), push(9), pop(), pop(), pop(), push(6). What is at the top of the stack now?