If 6 men and 8 boys can do a piece of work in 10 days while 26 men and 48 boys can do the same in 2 days, the time taken by 15 men and 20 boys in doing the same type of work will be `4\ d a y s` b. `\ 5\ d a y s` c. `6\ d a y s` d. `7\ d a y s`