A can do piece of work in 30 days while B can do it in 40 days. In how many days can A and B working together do it ?
A. 70 days
B. 120/7 days
C. 50 days
D. 45 days
A can do piece of work in 30 days while B can do it in 40 days. In how many days can A and B working together do it ?