You are wright about the height. From there you can calculate the potential energy.
Watch out for velocity since it's different from inicial velocity. As the stone falls it gains velocity.
I should've add that if you compute the energy at the top you get the total energy of the system. Once...
If I tell you that potential energy is "converted" into kinectic energy during fall. That at the edge of the cliff (155m) kinectic energy equals zero and potential energy is max. At the bottom of the cliff, kinectic energy is max wright before landing and potential is zero also before landing...