[" 2.A box of mass "8kg" is placed on a rough inclined plane "],[" of inclination "theta." Its downward motion can be prevented "],[" by applying an upward pull "F" and it can be made to slide "],[" upwards by applying a force "2F." The coefficient of friction "],[" between the box and the inclined plane is "],[[" a."(tan theta)/3," b."3tan theta," c."(tan theta)/2" d."2tan theta]]