A and B can do a piece of work in 30 days and 40 days, respectively. They began the work together but after a certain time, A leaves off and B completed the remaining work in 25 days. After how many days did A leave?
1
\(6 \frac{3}{7} \)
2
\(5 \frac{3}{7} \)
3
\(5 \frac{2}{7} \)
4
\(6 \frac{1}{7}\)