Task: Question Answering
Input (English): Problem: a can do a piece of work in 5 hours ; b and c together can do it in 3 hours , while a and c together can do it in 2 hours . how long will b alone take to do it ? 
Options: a ) 30 , b ) 20 , c ) 10 , d ) 6 , e ) 5
Output (English): a