Specific Heat Capacity and Energy

[Mukilab]

Homework Statement

http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2006_QP.pdf

Q15b

Answers:
http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2006_MS.pdf

I am confused on how the answer is reached, specifically how the formula energy needed=power/rate of reduction is laid out

Homework Equations

energy needed = power/rate of reduction

The Attempt at a Solution

What I am confused about is that since power is in J/s and rate of reduction is in kg/s that would make Energy needed into J/kg... or specific heat capacity and not energy itself.

How does this work?

 

[Mukilab]

Nevermind I realized that since the kg is 1, j/kg gives joules anyway