A 5kg block rests on a rough 30∘ incline. The coefficients of static and kinetic friction between the block and the plane are μs=0.40 and μk=0.30 respectively. The block is connected by a light string over a frictionless pulley to a hanging mass m. The minimum value of m (in kg) that will just start pulling the block up the plane is closest to (take g=10m s−2, sin30∘=0.5, cos30∘=0.866)
a) 6.1
b) 3.8
c) 4.2
d) 2.5