For lunch, Maria eats only salads or vegetarian burgers. Her weekly food budget is $36. Each salad costs $6 and each vegetarian burger costs $3. When deciding how much of each good to buy, Maria knows that 4 salads and 4 vegetarian burgers will give her a utility of 8. She also knows that at this level, her marginal utility per dollar spent is the same for both items. Maria's utility-maximizing point is: