{(Subscript[𝒟, 1]),(Subscript[𝒟, 2]),(Subscript[𝒟, 3]),(Subscript[𝒟, 4])}={ExponentialDistribution[1],ExponentialDistribution[2],WeibullDistribution[1,2],ErlangDistribution[1,2]};
ℛ=ReliabilityDistribution[(x∨y)∧(z∨v),{{x,(Subscript[𝒟, 1])},{y,(Subscript[𝒟, 2])},{z,(Subscript[𝒟, 3])},{v,(Subscript[𝒟, 4])}}];
bi=BirnbaumImportance[ℛ,t];
style=ColorData[1,"ColorList"];
Labeled[Plot[bi,{t,0,4},Filling->Axis,PlotRange->{0,1},Epilog->Inset[PieChart[bi/.t->3,ChartLabels->{x,y,z,v},PlotLabel->"t=3",SectorSpacing->{0.1,0},Background->White,ChartStyle->style,ChartBaseStyle->FaceForm[Opacity[0.7]],Frame->True,FrameTicks->None,FrameStyle->LightGray],{4,1},{Right,Top},{1.5,1.5}],Mesh->{{3}},MeshShading->{Automatic,LightGray},FillingStyle->Opacity[0.04],PlotStyle->style,ImageSize->Medium],Style["Improve x or y for maximum reliability","Graphics","Medium"]]