Two boxes A and B, each having a weight of 160 lb, sit on the 500-lb conveyor which is fre...

Two boxes A and B, each having a weight of 160 lb, sit on the 500-lb conveyor which is free to roll on the ground. If the belt starts from rest and begins to run with a speed of 3 ft/s, determine the final speed of the conveyor if

(a) the boxes are not stacked and A falls off then B falls off, and

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(b) A is stacked on top of B and both fall off together.