Science questions?

Question

A crane uses a block and tackle to lift a 2200 N flahstone to a height of 25 m.
b. In the process, the cranes hydraulic motor does 110 kJ of work
on the cable in the block and tackle. What is the effiency. (Just checking i got 2%)

c. What is the potential energy of the flagstone when it is 25 m above the ground? (On this one I could not find mass)

Answer 1

c. Potential energy = w*h = 2200 N * 25 m = 55000 j.
Note you don't need the mass because you have the weight. If you used the mass you'd have to multiply it by g to get weight, because energy = force (or weight) * distance (or height).
b. Efficiency = 55000/110000 = 50%

Answer 2

You weren't told otherwise, so it's reasonable to assume (and state your assumption) that this takes place on the surface of the earth. You know the acceleration of gravity there, so you know the relation between weight and mass.