A block rests on a rough inclined plane making an angle of 30∘ with horizontal. The coefficient of static friction between the block and inclined plane is 0.8. If the frictional force on the block is 10 N, the mass of the block in kg is ( g=10 m/s2 )
a. 2.0
b. 4.0
c. 1.6
d. 2.5