Answer: 64 kobos for 8 hours
Step-by-step explanation:
To calculate the cost of running the bulbs for 8 hours, we need to first determine the total energy consumed by the bulbs.
Energy consumed by the 40-watt bulb in 8 hours = 40 watts * 8 hours = 320 watt-hours
Energy consumed by one of the 60-watt bulbs in 8 hours = 60 watts * 8 hours = 480 watt-hours
Total energy consumed by the two 60-watt bulbs in 8 hours = 2 * 480 watt-hours = 960 watt-hours
Total energy consumed by all three bulbs in 8 hours = 320 + 960 = 1280 watt-hours = 1.28 kilowatt-hours (kWh)
Now, to calculate the cost of running the bulbs for 8 hours, we need to multiply the total energy consumed (1.28 kWh) by the cost of one unit (50 kobo).
Cost of running the bulbs for 8 hours = 1.28 kWh * 50 kobo/kWh = 64 kobo
Therefore, it will cost him 64 kobos to keep the bulbs lit for 8 hours