Task: Question Answering
Input (English): Problem: b completes a work in 3 days . a alone can do it in 10 days . if both work together , the work can be completed in how many days ? 
Options: a ) 2.31 days , b ) 4.31 days , c ) 5.31 days , d ) 6.31 days , e ) 7.31 days
Output (English): a