Given the data below, what is the after-tax cost of debt for Topstone Industries if its debt consists of 5-year bonds rated AA- and the tax rate is 50%? The Treasury yield is 5.19%.

	Corporate spreads
Rating	3 yr	5 yr	10 yr	30 yr
AAA	15	22	30	55
AA+	20	32	40	60
AA	30	37	50	65
AA-	35	45	55	70
A+	45	58	65	79
A	58	65	75	90
A-	79	85	88	108

		3.12%
		2.73%
		5.64%
		2.82%
		4.85%