min and max are declared inside the for loop and so are not in scope for the return statement.
P.S. Please be sure to use code tags when posting code to the forums. Unformatted or unindented code is extremely hard to read and many people that might be able to help you will just move along to posts that are easier to read. Please click this link ⇒ UseCodeTags ⇐ for more information. Properly indented and formatted code greatly increases the probability that your question will get quicker, better answers.
I've gone ahead and added the code tags for you. See how much easier the code is to read?