Explanation: To determine the line current, we must first convert the motor's mechanical horsepower output into electrical input power, accounting for both efficiency and power factor. 1. **Convert horsepower to watts (output power):** One horsepower (HP) is equivalent to 746 watts. Output Power (P_out) = 7 HP * 746 watts/HP = 5222 watts. 2. **Calculate electrical input power (P_in) considering efficiency:** Efficiency = P_out / P_in. Therefore, P_in = P_out / Efficiency. P_in = 5222 watts / 0.95 = 5496.84 watts. 3. **Calculate the line current (I) considering voltage and power factor:** For AC circuits, Input Power (P_in) = Voltage (V) * Current (I) * Power Factor (PF). Rearranging for current: I = P_in / (V * PF). I = 5496.84 watts / (120 V * 0.8) = 5496.84 watts / 96 V = 57.25875 amps. Rounding to one decimal place, the line current is approximately 57.3 amps. Answer D, 57.2 amps, is the closest option. This calculation demonstrates fundamental electrical principles crucial for understanding power consumption and supply requirements for various equipment, including those in an amateur radio shack, where efficiency and power factor can impact circuit design and operation.