'A' alone can do a piece of work in 10 days and 'B' alone can do it in 15 days. 'A' and 'B' undertook to do the work for ₹42,000. With the help of 'C', they completed the work in 5 days. How much (in ₹) is to be paid to C?

A

7,000

B

15,000

C

14,000

D

21,000