“How much extra gasoline will I need to pull my 5th wheel from Los Angeles through the mountains to Phoenix, then to Tucson? According to the map I’m looking at, the mountains look really big around Phoenix” asked the caller.
This is basically a flat 500 mile trip, perhaps a change in elevation of 500 feet or so to Phoenix and a descent to Tucson.
Of all the amazing things a chamber of commerce can do, calculating fuel usages isn’t one of them.