A and 13 together can do a piece of work in 12 days: B and C can do it in 20 days whilci C and A can do it in 15 days. A. B and C all working together can do it In
(a) 6 days
(b) 9 days
(c) 10 days
(d) 1012 days
A and B can do a piece of work in 18 days. B and C can do it in 24 days while C and A can finish it in 36 days. In how many days can A,B,C finish it. if they all work together?