We have $W = 10 + 0.895m -12.33c^{0.18} + 12.33c^{0.18}$
we calculate the differential of m, which is $0.895$ and the differential of $c$, which is something like $-12.33/c^{0.82} + 12.33/c^{0.82}$ and what then?
what do we do with $c$. I am confused...