The Gravitationa potential energy of the mass (PEG) is given by:
where
m is the mass
g is the gravitational acceleration
h is the heigth of the mass above the reference level (the ground)
In this problem,
and 
, therefore the gravitational potential energy of the mass is:
where
m is the mass
g is the gravitational acceleration
h is the heigth of the mass above the reference level (the ground)
In this problem,