r=SurvivalFunction[GompertzMakehamDistribution[λ,ξ],t];
rs=r r;
rp=1-(1-r) (1-r);

Block[{λ=2,ξ=.3},
Plot[{rs,rp},{t,0,2},PlotStyle->Thick,ImageSize->400,BaseStyle->{FontFamily->"Helvetica"},PlotLabel->"Reliability in series and in parallel",Epilog->{Inset[Framed[Style["in parallel",12],Background->LightYellow],{0.7,0.6},{Left,Bottom}],Inset[Framed[Style["in series",12],Background->LightYellow],{0.6,0.3},{Right,Top}]}]]