Hi,
Pl. Refer to Exercise No.4.31, page no- 306 for which data is referred from the example 4.11. (I attached this page)
Here in this problem Ri, R0, Av0, Ais and Gm will be same and it doesn’t depend on Rsig and RL.
As per problem Exercise 4.31:
1. When Rsig and RL is changed: In this problem, no information about the vi and vo is given. I can find these vi and v0 only for RL = ∞ condition. For RL = ∞, I got vi = 8.18mv and vo= 81.8mv. When RL is connected then how can I find Rin, Gv and Rout?

Thank you.

No it's not a home work problem. It's a matter of my own interest and i am not finding any ways to solve it.

@Alexander: Thank you for your reply. I repeat here again, the problem which i posted is not a home work problem. Getting to know the procedure to solve these type of problems only helps me to strengthen my basic understandings.

Still my doubts are not cleared yet.

part a) When Rsig changes:
If Rsig changes then surely vi also changes then CURRENTin also changes. Do you feel like, the changes in vi and the current (which is flowing into the two port) is same hence Rin doesn't change or bcz of any other reason?

part b) When RL changes:
When this happens, vo changes hence similarly Av (But Avo is constant) and also vi. As vi changes and also the current (into two port)and hence Rin has to be changed. But the problem here is that, neither i know vo nor vi or the current flowing in to the two port => unknowns are vi,vo,Rin,current (into two port) when load is connected. How can i find Rin with these many unknowns (only known thing is Av which can be calculated from Avo, Ro and RL)?

Note: if i assume Rin to be constant (As you told to keep every parameter constant)then  it doesn't match the answers given. In part (b) & (c) of exercise 4.31, Rin also changed by changing RL.