up[gams_]:=40 +.5 gam^2 
down[gams_]:=40- gam^2

g1 = Plot[{up[gams_]},{gam,0,5},PlotStyle->{Black,Thickness[Medium]},AxesLabel->{"Time","GDP"}, AxesOrigin ->{0,0},Filling->40,FillingStyle->RGBColor[0.3,0.4,0.2,0.2]];

g2 = Plot[{down[gams_]},{gam,0,5},PlotStyle->{Black,Thickness[Medium]},AxesLabel->{"Time","GDP"}, AxesOrigin ->{0,0},Filling ->40,FillingStyle->RGBColor[0.3,0.4,0.2,0.1]];
t1 = Graphics[Text["Money endogenous",{4.3,43}]];
t2 = Graphics[Text["Money exogenous",{4.3,33}]];
t3 = Graphics[Text["u = 1",{4.3,52.5}]];
t4 = Graphics[Text["u < 1",{4.3,17}]];
Show[g1, g2,t1,t2,t3,t4]