The ABCD matrix for a two-port network is defined by
[V1I1]=[ABCD][V2−I2]
The parameter B for the given two-port network(in ohms, correct to two decimal places) is
B=−V2I2∣∣∣V2=0
When V2=V2 (i.e., when port-2 is short circuited).
I1=V12Ω+(5Ω||2Ω)=7V124Ω
I2=−I1×5Ω5Ω+2Ω=−5V124Ω
So,B=−V1I2=245Ω=4.80Ω