Two horizontal forces F1 and F2 act simultaneously on a block of mass m as it slides in a straight line through a displacement s. F1 acts in the direction of motion while F2 acts opposite to it. Which one of the following expressions gives the change in kinetic energy of the block after the displacement?
a) 2(F1−F2)s
b) F1s
c) (F1−F2)s
d) (F1+F2)s