Task: Question Answering
Input (English): Problem: a and b can do a work in 5 days and 10 days respectively . a starts the work and b joins him after 4 days . in how many days can they complete the remaining work ? 
Options: a ) 6 days , b ) 2 / 3 days , c ) 8 days , d ) 3 days , e ) 9 days
Output (English): b