6. Why do we trade with other Nations? 7. (Marginal Analysis) The owner of a small pizzeria is deciding whether to increase the radius of delivery area by one mile. What considerations must be taken into account if such a decision is to increase profitability? 8. (Rational Self-Interest) If behavior is governed by rational self-interest, why do people make charitable contributions of time and money? 9. (Association Versus Causation) Suppose | observe that communities with lots of doctors tend to have relatively high rates of illness. I conclude that doctors cause illness. What's wrong with this reasoning