5. You are dragging a 110 kg trunk across a floor at a constant velocity with a horizontal force of 380 N. (a) Calculate the coefficient of kinetic friction. (b) A friend decides to help by pulling on the trunk with a force of 150 N [up]. Will this help? Calculate the force required to pull the trunk at a constant velocity to help you decide. (c) Instead of pulling on the trunk, your 55 kg friend just sits on it. What force is required keep the trunk moving at a constant velocity?