Calculating Op Amp Circuit Parameters

[ME_student]

Homework Statement

The op am in the circuit shown is ideal. Calculate the following.
a) Ia
b) Va
c) Vo
d) Io

Homework Equations

I have found three equations one at Vn, Va, and Vo.

The Attempt at a Solution

The attempt solution is on the attachment. I currently have three equations with four unknowns. I think I need to find a constraint equation, but not sure where to obtain it from. The constraint equation I have on attachment for Io valid?

 

[gneill]

Use the properties of an ideal op-amp to determine the voltage Vn. That will give you the information you need to determine the current through the 8k resistor and hence i_a. Continue with Ohm's Law and Kirchhoff's Laws to determine the rest.