Pipe A can fill a tank in 4 hours while pipe B can fill the tank in 6 hours. If they are opened on alternative hours, and if pipe A is opened first, in how many hours shall the tank be full?
1
\(4\frac{2}{3}\)
2
\(3\frac{1}{4}\)
3
\(4\frac{1}{2}{\rm{}}\)
4
\(3\frac{1}{2}\)