Solve the each part of given problem:
Problem: On the bunny hill at a ski resort, a towrope pulls the skiers up the hill with constant speed of 1.57 m/s. The slope of the hill is 10.7° with respect to the horizontal. A child is being pulled up the hill. The coefficients of static and kinetic friction between the child's skis and the snow are 0.149 and 0.106, respectively, and the child's mass is 61.3 kg, including the clothing and equipment.
Part A: What is the force with which the towrope has to pull on the child before movement, right as the child grabs the towrope?
Part B: What is the force with which the towrope has to pull on the child after movement begins?
Please explain clearly with details so that I can follow.