Subject: mathqa
Question: each of the three people individually can complete a certain job in 3 , 5 , 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 ?
Option: 
A: 5 / 18
B: 11 / 30
C: 7 / 18
D: 7 / 30
Answer: B