Arin alone can do a piece of work in 6 days and Selvi alone can do the same in 8 days. Arin and Selvi undertook to do it for Rs. 7,200. With the help of Kevin, they completed the work in 3 days. How much is to be paid to Kevin?
1
Rs. 900
2
Rs. 700
3
Rs. 800
4
Rs. 600