Various methods of calculating rates
The more professional amongst us, use a very complex computer program, that takes all the variables into account. The the computer operator will add a small percentage as hope money... " I hope they go for it..."
Or
at 3am, the same operator will say...last time it was x$, today is the same.
Or
My method, a piece of string, and a wall map of service area, on wall. the string is calibrated in hundreds or thousands of $$$$$.
The I add a fixed night stop figure. Then I shout it to the client, by E Mail or carrier pigeon.
Always works, and never actually proved to be wrong, (swings and roundabouts.)
glf