
Answer:
29223.6J
Explanation:
Given parameters:
Mass of Piano = 852kg
Height of lifting  = 3.5m
Unknown:
Gravitational potential energy  = ?
Solution:
The gravitational potential energy of a body can be expressed as the energy due to the position of a body;
 G.P.E  = mgh
m is the mass
g is the acceleration due to gravity
h is the height
 Now insert the given parameters and solve;
  G.P.E  = 852 x 9.8 x 3.5 = 29223.6J