We compute the change in net rate as a function of time.

Input := 


dnet[t_,s_] = D[net[t,s],t];

Input := 


setStuff = {};

Do[setStuff = Append[setStuff,

	{.0001 i,net[t,.0001 i]}/.FindRoot[dnet[t,.0001 i]==0,{t,2,4}][[1]] ],

			{i,0,400,10}]

setPlot = ListPlot[setStuff,PlotStyle->PointSize[.01],

        PlotRange->{{0,.05},{0,2.0}},

		AxesLabel->{"Energy cost ($/min)","MaxNet"}]

Output =


-Graphics-

Input := 


d[x_] = Fit[setStuff,{1,x,x^2},x]

Output =


                               2

1.98833 - 28.4241 x + 130.896 x

Input := 


dPlot = Plot[d[x],{x,0,.05}]

Output =


-Graphics-

Input := 


Show[setPlot,dPlot]

Output =


-Graphics-