A24 kg rock is resting on the floor. how much potential energy does it have?

Relative to the floor it's resting on, its height is zero,
so its potential energy is zero.

Relative to the next floor down, its height could be
three or four meters, and it could have plenty of
potential energy ... if you cut out a circle in the floor
all around the rock, and let it fall to next floor down,
it could really do some damage.  Look out below ! !