Feldspar Inc. is considering the capital structure for a new division. Management has been given the following cost information:

Debt/assets. kd(BT Cost of Debt). ke(Cost of Equity)

.35. 7%. 13%

.40. 7.5%. 13.6%

.45. 8%. 13.8%

.50. 9%. 14.6%

.55. 10.5%. 16.75%

Based on this information, what capital structure (debt/asset ratio) should management accept? Assume the marginal tax rate is 30%.