P, Q, and R can finish a work in 5 days, 10 days, and 15 days, respectively, working alone. P and Q work on the first day, P and R work on the second day and P and Q work on the third day, and so on till the work is completed. In how many days the work will be completed?
1
\(\frac{13}{2}\)
2
\(\frac{9}{2}\)
3
\(\frac{7}{2}\)
4
\(\frac{5}{2}\)