A 0.020kg bullet traveling 300m/s horizontally embeds in a 2.0kg cart that is initially at rest on a horizontal track. Immediately after the collision, the cart slides onto a 0.50m-long rough section and comes to rest at the end of that section. Assuming the coefficient of kinetic friction μk is constant on the rough section and negligible elsewhere, which value is closest to μk?
a) 0.60
b) 0.18
c) 0.90
d) 0.45