Total power consumption = 80 + 100 + 120 = 300W
P in KW = 0.3KW
Energy consumed = 0.3 x 6 = 1.8KWh
Monthly energy consumption = 1.8 x 31 = 55.8KWh
Cost of Monthly energy usage = 55.8 x 24.08 = #1343.664k ( since 1kwh = #24.08k)