On January 1, a company issued 8%, 20-year bonds with a face amount of $80 million for $72,639,456 to yield 9%. Interest is paid semiannually. What was interest expense at the effective interest rate on June 30, the first interest date? (Enter your answers in whole dollars. Round percentage answers to 1 decimal place (e.g., 0.0234 should be entered as 2.3).)