Lets assume that they are driving at an average of 70mph, and getting gas takes 10 minutes, and stopping to eat takes 30.
t=d/s
t=600/70
t=8.57
Stopping to eat twice is 30 x 2 = 60 (another hour)
and Gas is 10 x 3 = 30 minutes (0.5 hours)
Total time is,
8.57+1+0.5 =10.07
So the trip will take approx 10.7 hours total.
(This is using my assumptions, from my experience!)