(a) How does self-interest promote social interest? Provide a real-world example to support the answer. (b) What are the four factors of production? Which is the most important and why? (6 marks) (c) Suppose we are analysing the market for hot chocolate. What will be the impact on the equilibrium price and quantity of each of the following events affecting the hot chocolate market? (i) Consumer income falls because of a recession. (ii) The Surgeon General of Singapore announces that hot chocolate cures acne. (iii) Population increases and a better method of harvesting cocoa beans is introduced. (d) Explain why the law of demand is not violated when you observe the quantity demanded of chocolate and cocoa products at the shopping mall is higher in December than in June even though the price is higher in December than in June. (6 marks)