A spring (with a force constant of 225N/m) is resting on a horizontal(frictionless) surface and is mounted on a wall. A 1.5kg box is pushed against the spring compressing it 12.0cm from equilibrium. When released, the spring pushes the box. a)how much force must be exerted on the spring to compress it 12.0 cm? b)how much work is done on the spring to compress it 12.0 cm? c)how much elastic potential energy is stored in the spring it is compressed? d) Once released, what maximum speed will the box attain?