35. A sofa of weight 150 lb. rests on the floor. A horizontal force of 50 lb. is the smallest force that can make the sofa slide. (Assume static dynamic) a) What is the static friction coefficient between the sofa and the floor? b) What would be the acceleration of that sofa if pushed by a horizontal force of 60 lb? c) What would be the smallest force needed to push that sofa if a person whose weight is 180 lb. lies on it?