Exclude a Certain Value from the "Average" Function?

Hello, everyone, I am requesting help with a formula. I have a very basic, easy, rudimentary spreadsheet that keeps track of my electric bills.

Attached to this message is a copy of the spreadsheet. As you can see, it has a cell for the average of all the bills.

What I'd like to do is create a cell that displays the average for all the bills that are under 90 dollars (which are all part of Column B). I'd like to exclude from this calculation any and all bills that are $90.00 and over. I'm not sure how to do that.

Do I use the Averageif or Averageifs options? Or do I just need to modify the Average option?

Thank you. M. Pendleton