help calculating a diffusion rate using Fick's equation.

Wek

1. The problem statement, all variables and given/known data

Assuming:
Organism weight = 25 g
Organism lenght = 30 cm
[Na+ (ECF)] = 200 mM
[Na+ (water)] = 500 mM
ΔX(gill) = 6 μm
ΔX(skin) = 25 μm
A(gill) = 5.0 cm^2/gm
A(skin) = 10 cm^2/gm
Dk(gill) = 2 X 10^4 cm^2/s
Dk(skin) = 1 X 10^4 cm^2/s

Calculate the Na+ rate of diffusion through the skin using Fick's equation: (Dk)(A)((C1-C2)/dX)

2. Relevant equations

Fick's equation: (Dk)(A)((C1-C2)/dX)

3. The attempt at a solution

I'm not sure too sure if the answer that I'm getting is right. It seems to be too high and the units seem confusing.

Rate = (1 X 10^4)(10)((500-200)/25*10000) = 120 cm^3*mM/s*gm.

I am not sure if I should also use the weight and the length of the organism.

Thanks