4. (20 total) A 100-kg box is pulled at constant speed up a 10 loading ramp by a strap, as shown. The strap is angled 30 above the top surface of the box. The coefficients of friction between the box and the ramp are k = 0.4 and s = 0.6. 10 30 a. (8 pts) On the dot above, draw a free body diagram for the box. Label each force, and clearly indicate your coordinate system. b. (12 pts) What tension is required in the strap to keep the ox moving at constant speed up the ramp?