Task: Question Answering
Input (English): Problem: george does 3 / 5 th of a piece of work in 9 days . he then calls in paul and they finish the work in 4 days . how long would paul take to do the work by himself ? 
Options: a ) 10 , b ) 20 , c ) 30 , d ) 40 , e ) 50
Output (English): c