On some days, Gustav makes his own salad for lunch, preferring to use either iceberg or romaine lettuce, topped off with lots of fresh tomatoes. For Gustav, the cross-price elasticity of demand for iceberg lettuce with respect to romaine lettuce is _____, and the cross-price elasticity of demand for iceberg lettuce with respect to tomatoes is _____. Question 16 Answer a. positive; negative b. negative; zero c. zero; positive d. negative; positive