P takes 3 days to complete 1/5th of work, Q takes 6 days to complete 1/2 of the work and R takes 6 days to complete the 2/3. If all three worked together for 3 days. Then P and Q left the work. The remaining work is completed by R in -
1
35/13 days
2
38/17 days
3
39/20 days
4
34/21 days