Task: Question Answering
Input (English): Problem: each of the three people individually can complete a certain job in 3 , 4 , and 6 hours , respectively . what is the lowest fraction of the job that can be done in 1 hour by 2 of the people working together at their respective rates ? 
Options: a ) 1 / 3 , b ) 9 / 20 , c ) 8 / 15 , d ) 5 / 12 , e ) 2 / 3
Output (English): d