As shown in the figure below, a box of mass m = 10.4 kg is released from rest (at position A) at the top of a 30.0° frictionless incline. The box slides a distance d = 4.80 m down the incline before it encounters (at position B) a spring and compresses it an amount xC = 0.280 m (to point C) before coming momentarily to rest. Using energy content, determine the following. (a) the speed (in m/s) of the box at position B vB = 1 6.86 m/s (b) the spring constant (in N/m) k = 2 N/m