Pipe 'P' can fill 3.5x2% of the tank in 14 minutes, pipe 'Q' can fill one-third of the tank in 4 minutes, and pipe 'R' can fill half of the tank in 24 minutes. If pipe 'P and 'Q' are opened together and after 4 minutes pipe 'Q' closed and pipe 'R' opened then pipe 'P' and 'R' together filled the remaining tank in 5 minutes. Find the time taken by pipe 'P' and 'R' together to fill the whole tank?
1
10 minutes
2
12 minutes
3
15 minutes
4
20 minutes
5
24 minutes