How high would a 20 kg mass have to be raised to have a gravitational potential energy of 1,000 J?

May someone explain how to do this question?

Determine the moment of the force f about an axis extending between a and c. express the result as a cartesian vector. a is at the origin, c is at (4,3,0) and f = (4i + 12j -3k) lb coming out of b (4,3,-2).

You can melt ice by applying pressure because the solid/liquid line has a slope.