For earthing an electrical appliance one has to remove the paint from the metal body of the appliance where the electrical contact is made. Explain the reason.

Calculate the electricity bill of a month of $30$ days in a house $220 V$ with the following appliances being used. Five $60 W$ bulbs for $6$ hours every day. The cost of the first $200$ units is Rs. $2.40$ and the next $200$units for Rs. $4$ per unit.

Calculate the electricity bill of a month of $30$ days in a house of $220 \mathrm{V}$ with the following appliances being used. $750 \mathrm{W}$ electric iron for $1$ hour every day, The cost of first $200$units are Rs.  $2.40$and next $200$units for Rs. $4$ per unit.

Calculate the electricity bill of a month of $30$ days in a house of $220 \mathrm{V}$ with the following appliances being used. Two $1000 \mathrm{W}$ heaters for $2$ hours daily, The cost of first $200$ units is Rs. $2.4$ and next $200$ units is Rs.$4$ per unit.