rrency is a medium of exchange for goods and services. Ashok made a payment to shopkeeper, for the article he purchased, in the denomination of ₹500 and ₹ 20. He paid ₹ 2640 to the shopkeeper. If all the denomination of ₹ 500 is to be changed by ₹ 100 then the boy could have paid ₹ 640 only. Assume the number of currency notes of ₹ 500 as ‘f’ and the number of currency notes of ₹ 20 as ‘g’. Based on the above information, answer the following questions: i) Write a linear equation representing the amount paid by Ashok.​