The firm has $7,500$ bonds outstanding with a face value of $$1,000$ per bond. The bonds carry a $9$ percent coupon, pay interest semiannually, and mature in $8$ years. The bonds are selling at $98$ percent of face value. The company's tax rate is $34$ percent. What is the firm's after$-$tax cost of debt?

$3\mathrm{.}42$ percent

$4\mathrm{.}84$ percent

$6\mathrm{.}18$ percent

$8\mathrm{.}25$ percent