Liz operates a high-tech bar. She can turn out either a smoothie or a salad every 2 minutes. If she spends all her time making smoothies, she produces 30 an hour. If she spends all her time making salads, she also produces 30 an hour (Table 3.1 ). If she splits her time equally between the two, she can produce 15 smoothies and 15 salads an hour. For each additional smoothie Liz produces, she must decrease her production of salads by one, and for each additional salad Liz produces, she must decrease her production of smoothies by one. So