Task: Question Answering
Input (English): Problem: working together , a and b can do a job in 6 days . b and c can do the same job in 10 days , while c and a can do it in 7.5 days . how long will it take if all a , b and c work together to complete the job ? 
Options: a ) 4 days , b ) 5 days , c ) 8 days , d ) 9 days , e ) 10 days
Output (English): b