A company is planning to spend up to $10,000 on advertising. It costs $3,000 per minute to advertise on television and $1,000 per minute to advertise on radio.
If the company buys x minutes of television advertising and y minutes of radio advertising, its revenue in thousands of dollars is given by:
f(x,y) = -2x^2 - y^2 + xy + 8x + 3y
Find the values of x and y that maximize the firms revenue while staying within its advertising budget.