Car counting

I tried to estimate our car requirements. At any time there are about 90 cars at industries plus say 3 trains with 8 cars or another 24 cars or 114 cars in total with none in the yards, so add another 90 cars for the next day and you get 204 cars max. Cars needed. The total 2 top days in a row, for all car types is 198 cars. That puts 42 cars in each of the 2 yards, with 3 trains on the layout, that I would guess would be a good max. count. The total industry car count only varies by a max of 6 cars for any 1 car type, per day. Guessing the car count for any type will only drop by 10 or under, for the first 4 trains of the session, until trains start returning, maybe we could use 1/2 the next highest count for the min. Cars required. This works out to 46 to 58 box cars, 31 to 43 hoppers, 18 to 24 covered hoppers, 14 to 17 flat cars, 10 to 13 gons, 8 to 10 refers, 19 to 23 tankers, 8 to 10 stock cars or 154 min to 198 max. That means at the min. count there would be 20 cars in each yard with 3 trains running, a much better number. This does not include piggyback cars and sawdust cars maybe a total of 5 cars. I have no idea how close we are, but I would guess we are close to the min.