To complete a certain work, A and B together take 15 days; B and C together take 12 days, and C and A together take 10 days. All the three worked together for 6 days, then B and C left. A alone will complete the remaining work in
1
6 days
2
\(8 \dfrac{1}{2} \ \rm{days}\)
3
9 days
4
\(7 \dfrac{1}{2} \ \rm{days}\)