12 USC 412: “Any Federal Reserve bank may make application to the local Federal Reserve agent for such amount of the Federal Reserve notes hereinbefore provided for as it may require. ” As you may require, which are necessities.
Check Clearing for the 21st Century Act, Section 3, Section 3, Definitions. (2). BANK — The Term “bank” means any person that is located in a State and engaged in the business of banking…”