no im sure its C because effeciency=work/energy input
and we all know work=ke=0.5mv^2 and energy input is worke done by driving force which is equal to Fs
0.5mv^2/Fs = mv^2/2Fs
it had nothing to do with mgsin because its energy and mass not weight
and even if it was constant so? just keep it 0.5mv^2 you still have a velocity
though you have a point ima_shah2002
yes i can if someone can remind me of the values