I do not need help with a, I just need to figure out the coefficient of friction in this and I do not know how.

After a big snowstorm, Steven decides to go out to have some fun, and slides down a hill. Once at the bottom, he eventually slows down from a speed of 3.5 m/s to 1.3 m/s in 6 seconds. a. Draw a free body diagram for Steven when he is at the bottom of the hill. Label your forces and make the vector lengths accurate. (3 pts)