Alemon with mass 0.3 kg falls out of a tree from a height of 18 m. how much mechanical energy does the lemon have just before it hits the ground?

Answer is: the objects mechanical energy is 52,92 J.
m(object) = 0,3 kg.
h(object) = 18 m.
g = 9,8 m/s².
E(object) = m·g·h.
E(object) = 0,3 kg · 9,8 m/s² · 18 m.
E(object) = 52,92 N·m = 52,92 J..
g - the acceleration of free fall.
mg - weight of the object.

thats how its supposed to be