For the signal flow graph shown below, the transmittance

Here forward paths are
P1 = rsu, P2 = efh
apply Manson's gain formula,
gain = x₂/x₁
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P₁Δ₁ + P₂Δ₂Δ
where,
Δ₁ = (1 – fg)
Δ₂ = (1 – st)
= 1 – (fg + st) + fgst
so,

x₂	=	rus (1 -fg) + efh(1 - sf)
x₁	=	1 - (fg + st) + fgst

x₂	=	rus (1 -fg) + efh(1 - sf)
x₁	=	(1 - st) (1 - fg)

x₂	=	rus	+	efh
x₁	=	1 - st	+	(1 - fg)

rsu	+	efh
1 - st	+	1 - fg

rsu	+	efh
1 - fg	+	1 - st

efh	+	rsu
1 - ru	+	1 - eh

rst	+	rsu
1 - eh	+	1 - st