(5 bulbs) x (25 watt/bulb) x (6 hour/day) x (30 day/month) =
(5 x 25 x 6 x 30) watt-hour/month =
22,500 watt-hour/month .
The most common unit of electrical energy used for billing purposes
is the 'kilowatt-hour' = 1,000 watt-hours .
22,500 watt-hour/month = 22.5 kWh/month.
(22.5 kWh/month) x (1.50 Rs/kWh) = 33.75 Rs / month