A tube A of radius r is connected to two other tubes B and C with the help of a junction valve. The tubes B and C have radii `(r )/(2)` and `(r )/(3)` and the flow velocity in each is v and 3v resopectively. If the flow velocity in tube A is `(n)/(m)v`, when n and m are integers, then what is the value of `n+m` ?