Gravitational Potential Energy Question

How much more gravitational potential energy does a 1.4kg hammer have when it is on a shelf 1.4m high than when it is on a shelf 0.70m high?

thank you!

Difference in PE (gravitational)= mgh-mgh= (1.4)(1.4)(9.8)-(1.4)(.70)(9.8)

∆P = mg∆h
= (1.4 kg)(9.81 m/s²)(1.4 - 0.70)m
= 9.6 J