work: w = fd (given)
work done by chet =50*1 = 50 j
work done by mika =40*2 = 80 j
work done by sara =30*1.5 = 45 j
work done by bill =60*0.5 = 30 j
students in order from the greatest amount of work done to the least is mika> chet> sara> bill
hence option (b) is correct.