Refer to the original data. Assume again that the company sold $28,000$ units last year. The president feels that it would be unwise to change the selling price. Instead, she wants to increase the sales commission by $$2$ per unit. She thinks that this move, combined with some increase in advertising, would double annual unit sales. By how much could advertising be increased with profits remaining unchanged? Do not prepare an income statement; use the incremental analysis approach.