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
How can the firm maximize its revenue?