A small block starts slipping down from a point B on an inclined plane AB, which makes an angle θ with the horizontal. Section BC is smooth and the remaining section CA is rough with coefficient of friction μ. The block comes to rest as it reaches the bottom (point A) of the inclined plane. If BC=2AC, and μ=ktanθ, find k.
a. 1
b. 2
c. 3
d. 4