Admittance parameters and input impedance

[quick]

http://img420.imageshack.us/img420/9300/img02643tt.jpg

hello this is the problem i am working on. i started out by using the admittance parameter equation

i1 = y11*v1 + y12*v2
i2 = y21*v1 + y22*v2

so i1 is 20/50 by ohms law. so i1 = 0.4 so by the first equation i get v2 = 32 V.
also plugging in values for the second equation i get i2 = 0.2 A.
finally i got V0 by -I2*50ohms to get -10V.

the second part about the input impedance is where i run into trouble because of the dependent source.

 

[SGT]

You did it wrong. The current through Vo is I2 + 0.2*V1.
The input impedance is Zi = V1/I1.
I did not make the other calculations but I think they are wrong. For instance, where did you get I1 = 20/50?