Consider a city of 100 people (50 old people and 50 young people) and two neighborhoods (50 available lots in each). People generally prefer to live close to old people because old people have wisdom that confer large positive externalities to other homes in their vicinity. The premium curves are as follows: Young people: r = 2n -40 Old people: r = 4n - 100 where r is the rent premium and n is the number of old people in the neighborhood of interest. a) Draw the two rent premium curves. (3 points) b) Identify all possible equilibria. Which is stable, and which is unstable? Explain why that is the case. Show your work. (3 points)