Stack X is an empty stack. Please answer the questions below after tracking the activities below step by step:

X.push(4); X.push(3); X.push((7); Y1 = X.pop(); Y2 = X.pop(); X.push(2); X.push(3); Y3 = X.peek();

a. Y1 = __________________

b. Y2 = _________________

c. Y3 = _________________

d. X = __________________ (after all the above statements are executed, starting from the bottom of the stack).