For the circuit shown in Figure P18.30, use Kirchhoff's rules to obtain equations for

1. the upper loop,
2. the lower loop, and
3. the node on the left side. In each case suppress units for clarity and simplify, combining like terms.
4. Solve the node equation for I36?.
5. Using the equation found in (d), eliminate I36? from the equation found in part (b).
6. Solve the equations found in part (a) and part (e) simultaneously for the two unknowns for I18? and I12?, respectively.
7. Substitute the answers found in part (f) into the node equation found in part (d), solving for I36?.
8. What is the significance of the negative answer for I12??

Figure P18.30