An electric refrigerator rated $400 \mathrm{W}$ is used for $8$ hours a day. An electric iron box rated $750 \mathrm{W}$ is used for $2$ hours a day. Calculate the cost (in rupees) of using these appliances for $30$ days, if the cost of $1 \mathrm{kWh}$ is $₹3$.

There are $60 \mathrm{watt}$ lamp and $80 \mathrm{watt}$ fans in a house. The lamp and the fan run for $5 \mathrm{hours}$daily. Find out the expense in a month if a unit of electricity cost $\mathrm{Rs}.4/-$(Assume that one month$=30 \mathrm{days}$)

Soham uses a $600 \mathrm{W}$ Music System for $5$ hours daily. Calculate the electrical energy consumed in $\mathrm{kWH}$ for $30$ days.

The diagram below shows a dual control switch circuit connected to a bulb. Out of A & B which one is the live wire and which one is the neutral wire? 

A $200 \mathrm{W}$ bulb is lighted for $2$ hours. How much energy is consumed?