I honestly don't know how to start this problem and any help would be appreciated.
"In 1950 an experiment was done observing the time gaps between successive cars on the Arroyo Seco Freeway. The data show that the density function of these time gaps was given approximately by p(x)=ae^(-0.122x) where x is the time in seconds and a is a constant.
a) Find a."
That's not the whole question, but this is the one I'm confused about. How am I to find a, with little information?