The towers of a transmission line are 38 m tall. They are spaced 280 m apart and are joined at their tops by a single ground wire of surge impedance 520 N. The surge impedance of the towers themselves is 135 N. Lightning strikes the ground wire 100 m from a tower. The stroke current rises to a peak of 50 kA in 1.5 us. Determine the voltage of the closest tower top 0.75 pus after the lightning contacts the ground wire. Assume the impedance of the lightning channel is 1500 N and the footing resistance is 25 N. Waves on the tower travel at 90% of the speed of light.