Sales $ $1,120,000$

Variable expenses $560,000$

Contribution margin $560,000$

Fixed expenses $160,000$

Net operating income $ $400,000$

The president does not want to change the selling price. Instead, he wants to increase the sales commission by $$2\mathrm{.}50$ per unit. He thinks this move, combined with some increase in advertising, would increase this year's unit sales by $25\%.$ How much could the president increase this year's advertising expense and still earn the same $$400,000$ net operating income as last year?