Two-object force problems/Atwood's machine

Two blocks hang from opposite ends of a rope, and the rope passes over a pair of pulleys. One block has a weight of 412 N, and the other has a weight of 908 N. The rope and the pulleys are massless, and there is no friction. (a) What is the acceleration of the lighter block? (b) What is the tension in the rope? Suppose the 908 N block is removed, and you pull down on the rope with a force of 908 N. Find the acceleration of the lighter block.