a) 3 bulbs rated 40W for 5 hrs : 3*40*5 = 600 Watt hours
b) A heater rated 1500W for 3hrs 3* 1500 = 4500 Watt hours
c) A fridge rated 400W
Would assume the Fridge would run for 24 hours a day :400*24 = 9600 Watt hours
Total Watt hours for 1 day :
600 + 4500 + 9600 = 14700 Watt hours
Unit of Electricity is in kWh
14 700 wh = 14700/1000 = 14.7kWh
But 1kWh = Rs.3
14.7 kWh = 3*14.7 = 44.1
Total cost = Rs.44.10