A 4.0kg block is released from rest on a 30∘ rough incline. The coefficient of kinetic friction between the block and the surface is 0.20. Take g=9.8m/s2. What is the magnitude of the block’s acceleration down the slope?
a) 4.9m/s2
b) 3.9m/s2
c) 3.2m/s2
d) 2.9m/s2