The efficiencies of A, B and C are in the ratio 2 ∶ 5 ∶ 7 working together, they can complete a work in 10 days. In how many days will, A alone be able to complete 30% of that work?

The efficiencies of A, B and C are in the ratio 2 ∶ 5 ∶ 7 working

1.	The efficiencies of A, B and C are in the ratio 2 ∶ 5 ∶ 7 working together, they can complete a work in 10 days. In how many days will, A alone be able to complete 30% of that work?
A.	20
B.	28
C.	30
D.	21
Answer» E.