Simple Y-parameter (admittance-parameter) matrix problem?

[asdf12312]

simple Y-parameter (admittance-parameter) matrix problem??

Homework Statement

Homework Equations

general form of Y-parameter is
[I₁]=[Y₁₁ Y₁₂][V1]
[I₂]=[Y₂₁ Y₂₂][V2]

The Attempt at a Solution

i think i was confused what exactly this problem asked for. the general equation for I₁ for instance you would add the variables, so I₁=Y₁₁(V1)+Y₁₂(V2). to calculate Y₁₁ also, you would add a 1V source on the left side, and short-circuit the right side. so I'm pretty sure it would be Y₁₁=(\frac{1}{Ya}+\frac{1}{Yb})s. since the only signs i saw in these equations were '+' i put the 1st choice (A) as my answer.

 

[rude man]

A is the answer.

The idea is that, for two networks, the input currents i_1A and i1_1B are added and so are the output currents i_2A and i_2B . This implies that the individual admittance parameters y_ij for A and B are also added.