Two pipes, A and B, can fill a tank of 1000 litres in 5 hours and 6 hours, respectively. If they are opened together, how many hours will they take to fill an empty tank of 1800 litres?
1
\(\frac{54}{11}\)
2
\(\frac{52}{11}\)
3
\(\frac{25}{11}\)
4
\(\frac{45}{11}\)