You are working in a shoe test lab measuring the coefficient of friction for tennis shoes on a variety of surfaces. The shoes are pushed against the surfaces with a force of 400 N, and a sample of the surface material is then pulled out from under the shoe by a machine. The machine pulles with a force of 300 N before the materail begins to slide. When the material is sliding, the machine only has to pull with a force of 200 N to keep the material moving.
A. What is the coefficient of static friction between the shoe and the material?
B. What is the coefficient of dynamic friction between the shoe and the material?