I need help with understanding these questions

3-94 A wagon weighing 5 x 10' N is pulled along a muddy, horizontal road by a 500-kg horse. The coefficient of friction between the wagon wheels and the road is 0.2. (a) If the wagon is pulled at constant speed, what force must the horse exert on the ground to pull the wagon?If static friction between tires and road is 0.75. What is the maximum incline plane angle could be before car start to slide? Upload Choose a FileQuestion 16 3-99 A girl of mass 40 kg skis down a slope. which is at an angle of 37 with the horizontal (Neglect air resistance.) If the coefficient of ki- netic friction between her skis and the snow is 0.1. what is her acceleration