Find the bus admittance matrix (Ybus) for the 4-bus system in Figure 3. All four transmission lines are lossless (R = 0), with their series impedance (jX) values in p.u. are given in Figure 3. In addition, the line connecting buses 2 and 4 is a long one with shunt admittance of j0.12 p.u. in each leg of its π-circuit model, and same for the line between buses 3 and 4 with shunt admittance of j0.07 p.u. in each leg. The other two lines are short lines with no shunts.