Subject: mathqa
Question: gary drove from point a to point b at 60 km / h . on his way back he took a train travelling at 110 km / h and therefore his trip back lasted 5 hours less . what is the distance ( in km ) between a and b ?
Option: 
A: 690 .
B: 660 .
C: 630 .
D: 600 .
Answer: B