A worker drags a crate across a factory floor by pulling on a rope tied to the crate. The worker exerts a force of magnitude F = 450 N on the rope, which is inclined at angle ? = 42° to the horizontal, and the floor exerts a horizontal force of magnitude f = 140 N that opposes the motion. Calculate the magnitude of the acceleration of the crate if
(a) its mass is 320 kg and
(b) its weight is 320 N.