One formula to average specific criteria from data range

Hello,

As you will see with my sample workbook, I am trying to take the average of reimbursement %s from each prefix for each state. The workbook only reflects a fraction of the data I am working with, so my solution, as of now, takes quite a while to arrange, and involves a lot of copy and pasting and hiding rows to clean things up. I think that perhaps some type of combination of the IF, index match, and average functions may may my job a lot easier, but as of now, I have not been able to figure it out. Any suggestions?