A tank can be filled by a pipe P in 32 minutes and by pipe Q in 36 minutes. When it is full, it can be emptied by a pipe R in 20 minutes. If all the three pipes are opened simultaneously, half of the tank will be filled in ________.
1
\(55\frac{3}{5}\;minutes\)
2
\(55\frac{13}{3}\;minutes\)
3
\(55\frac{5}{13}\;minutes\)
4
\(55\frac{2}{5}\;minutes\)