4. For each example of an aggregated problematic outcome that I give you, (i) explain a decision individuals make which leads to an externality, (ii) describe this externality and explain how it contributes to the aggregated outcome, and (iii) explain what incentive we could give to people to avoid them making decisions that, in the aggregate, contribute to that outcome. (5 lines for each example should suffice) (a) Traffic jams in cities. (b) Air pollution in cities. (c) Racial segregation in city schools