here I am giving the code.
f[Subscript[Y, 0, A] _, Subscript[Y, 0, B] _, Subscript[\[Eta], A] _,
Subscript[\[Eta],
B] _, \[Lambda]_ ] = (1 - ((1 -
Subscript[Y, 0, A])/(1 +
Subscript[\[Eta], A]*\[Lambda])^2) - ((1 -
Subscript[Y, 0, B])/(1 +
Subscript[\[Eta], B]*\[Lambda])^2) + ((1 -
Subscript[Y, 0, A])*(1 -
Subscript[Y, 0, B])/(1 + Subscript[\[Eta], A]*\[Lambda] +
Subscript[\[Eta], B]*\[Lambda] -
Subscript[\[Eta], A]*Subscript[\[Eta], B]*\[Lambda])^2))
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