DeKay Dental Supplies issued $10,000 of 20-year bonds on January 1, 2021. The bonds pay interest semiannually. This is a partial bond amortization schedule for the bonds.

Payment Cash Effective interest Decrease in Balance Outstanding Balance
9,080
1 400 409 9 9,089
2 400 409 9 9,089
3 400 409 9 9,107
4 400 410 10 9117

Requied:
What is the stated annual rate of interest on the bonds?