4. Analyze the income and substitution effects of the impact of a falling price with a step by step reasoning. (16%)

(2) Assume that the modern society follows the two principles: "Lady first" and "reciprocity", which means they go to ballet together in the first round and then go to boxing together next time and so on. Show that the payoff of this "focal point" equilibrium is greater than that of mixed strategy. (6%)