Not spoiler description: Find the secret number, and make an equation equal to that secret number.
(If you don't want a spoiler, skip through and don't read the next message)
The secret number is 200.
i'm a bit late, but for the last lost multiplier, find the ''secret number'' file and then make that number the result of an equation in calculator (for example, if it's 50, do 5 x 10 or 25 + 25 or something)
The autobuyers seem to not work, buy some generators.