P can lay railway track between two stations in 16 days. Q can do the same job in 12 days. With the help of R, they completes the job in 4 days. How much days does it take for R alone to complete the work?	Choose the correct choice from the following answers:
A) 9 days  B) 9 (3/5) days  C) 11 1/5 days  D) 13 days  E) 13 1/7
Amount of work P can do in 1 day = 1/16   Amount of work Q can do in 1 day = 1/12   Amount of work P, Q and R can together do in 1 day = 1/4   Amount of work R can do in 1 day = 1/4 - (1/16 + 1/12) = 3/16 – 1/12 = 5/48   =&gt; Hence R can do the job on 48/5 days = 9 (3/5) days   9 (3/5) days)
<result>B</result>
P can lay railway track between two stations in 16 days. Q can do the same job in 12 days. With the help of R, they completes the job in 4 days. How much days does it take for R alone to complete the work?