Two winches, A and B, each operate continuously at 20kW. Winch A lifts a load at 0.50m/s, while winch B lifts an identical load at 1.25m/s. What is the ratio of the lifting force exerted by winch A to that exerted by winch B?
a) 0.4:1
b) 1:1
c) 2.5:1
d) 4:1