Answer: 1580 J
Step-by-step explanation:
Energy is in the form of gravitational potential energy. (GPE)
GPE = mgh , where m is the mass of the block, h is the height and g is the gravitational constant of 9.81 ms-2.
Hence,
Total energy = mass x gravitational constant x height
= Weight x height (since W = mg)
= 79 x 20 J
= 1580 J