Now that you watched the video, here is some information you might use to solve the problem!
Wikepedia - Exelerator
http://en.wikipedia.org/wiki/Xcelerator
Knott's Berry Farms Roller Coaster Specs
http://www.knotts.com/rides/Roller-Coasters-1-5-12-35/Xcelerator
Other information you might want to know:
I wanted to know how long it would take one group. I started timing when the group of 4 was allowed to load. I stopped the timer when the next group was allowed to load. The total time for this was 3:35 minutes.
There were 11 people in front of me.
4 people fit in the front car.
How long did it take me to get on the roller coaster?