Answer:
The amount of energy required is 
Explanation:
The energy required to convert the ice to steam is the sum of:
1) Energy required to raise the temperature of the ice from -20 to 0 degree Celsius.
2) Latent heat required to convert the ice into water.
3) Energy required to raise the temperature of water from 0 degrees to 100 degrees
4) Latent heat required to convert the water at 100 degrees to steam.
The amount of energy required in each process is as under
1) 
where
' is specific heat of ice =
2) Amount of heat required in phase 2 equals

3) The amount of heat required to raise the temperature of water from 0 to 100 degrees centigrade equals

where
' is specific heat of water=
4) Amount of heat required in phase 4 equals

Thus the total heat required equals 
The change in the gravitational potential energy is represented by the equation
u = ΔPE = Δmgh
since the mass of the system will remain constant and the acceleration due to gravity will also remain constant, the equation will become
u = mg Δh
If he's falling in a straight line and his speed is not changing, that tells you that his acceleration is zero.
And THAT tells you that the forces on him are balanced, the net force acting on him is zero, and his motion is the same as it would be if there were NO force acting on him.