Which controls (internal) would best mitigate the following threats?

a) Posting the amount of a sale to a customer account that does not exist.

b) A customer entering too many characters into the five-digit zip code while making an online purchase, causing the server to crash.

c) An intern's pay rate was entered as $150 per hour, not $15 per hour.

d) Approving a customer order without the customer's address so the order was not shipped on time.

e) Entering the contract number of a critical contract as 13688 instead of 16388, which is a serious mistake for the company.