A small community has only one bank, and it is locally owned.

A small community has only one bank, and it is locally owned.  This community has a lot of high-income families who save regularly so that it is a deposit-surplus area, that is, an area in which customers tend to deposit more money than can be loaned out locally. Even so, when interest rates rise nationally, this bank raises its interest rates. How does opportunity cost relate to this situation?