Last year, Cayman Corporation had sales of $7,000,000, total variable costs of $3,000,000, and total fixed costs of $1,500,000. In addition, they paid $480,000 in interest to bondholders. Cayman has a 35% marginal tax rate. If Cayman's sales increase 7%, what should be the increase in operating income? 10.8% 11.2% 8.7% 13.3\% 13.9%