Three pipes, A and B and C, can fill a tank in 15 hours, 12 hours, and 18 hours, respectively. If both pipes A and C are opened simultaneously into the empty tank, then the time taken (in hours) to fill the tank will be:
1
\(8\frac{2}{{11}}\)
2
\(6\frac{5}{9}\)
3
\(7\frac{2}{3}\)
4
\(9\frac{3}{5}\)