remember, the work is given by:

where is the force required to do the job of lifting an object from a height to

obviously and . the hard part is to find .

so lets think through this. it takes 20(9.81) N = 196.2 N of force to lift a 20kg bucket. but this force is changing, since water is leaking out. by the time we get to the top, 5 kg of water leaked out. the trip took 12 minutes, so that means the water is leaking at 5/720 = 1/44 kg/s. in other words, every second, the force we are lifting decreases by 1/44 kg = 0.068125 N.

now, can you tell me what is?