Madhavi bought a scooter for Rs.40,000 but she does not have enough money to pay all at once. The shopkeeper says that she can divide the cost into 4 equal monthly instalments but she would have to pay Rs.100 extra each month for 4 months. What is this additional amount paid by Madhavi to the shopkeeper called as and calculate the total extra amount at the end of 4 months paid by Madhavi?