A single-threaded 25-mm power screw is 25 mm in diameter with a pitch of 5 mm. A vertical load on the screw reaches a maximum of 6 kN. The coefficients of friction are 0.05 for the collar and 0.08 for the threads. The frictional diameter of the collar is 40 mm. (a) Find the torque to "raise" and "lower" the load (b) What is the overall efficiency? (c) Is the thread self-locking?