Just to estimate an answer (which you should always do in physics)
Givens
g = 9.81 (call it 10 for estimation purposes)
m = 966 (call it 1000 for estimation purposes)
h = 72 m
Ep = m*g * h
Ep = 1000 * 10 * 72
Ep = 720000 So this is about what you should get.
Exact answer
Ep = 9.81 * 966 * 72
Ep = 682305 which should be rounded to 2 places.
Ep = 6.8 * 10 ^5