Resistor Designations as follows:
The 2 input resistors on the left side are equal and labelled R1
The 2 resistors at the top of the T are equal and labelled R2
The 2 resistors at the bottom of the T are equal and also equal to those at the top therefore also labelled as R2
The vertical branch resistor is a fraction of the value R2, designated KR2
The Gain is then given by: G = 2*R2/R1*(1+(1/K))
If R1=R2 then: G= 2+(2/K) and if all resistors are equal G=4 as K is equal to 1 in that case
