Grouper Company is constructing a building. Construction began on February 1 and was completed on December 31. Expenditures were
$2,052,000 on March 1, $1,200,000 on June 1, and $3,007,200 on December 31. Grouper Company borrowed $1,042,720 on March 1 on a 5-year, 13% note to help finance construction of the building. In addition, the company had outstanding all year a 9%, 5-year, $2,039,800 note payable and an 10%, 4-year, $3,462,500 note payable. Compute the weighted-average interest rate used for interest capitalization purposes.