The efficiency of a machine is 80% calculate the work done by a person using the machine to raise a load of 300kg through a height of 4m (take g=10/s2)

work = force * distance

But you only get to use 80% of the work input. That means that
0.8W = 300*10*4

I need the answer

7500j

Efficiency=work out put/work input x 100

80/100=200 x 3 x 10/x
80x=600000
x=7500j

1500j

300×10×4×100/80

62500 i think