4. (20%) Consider a setting with two goods. Good 1 is food and its price is $4. Good 2 is shelter and the rental rate is $6. Sally has income $3000. She also receives food stamp which she may redeem for food up to amount $300 at the market price. Initially, Sally consumes 300 units of food (including those from food stamp) and spends the rest of her income on shelter. (a) Find out the initial quantity of shelter #2 Sally buys. Now suppose the price of food increases from $4 to $5. (b) Draw the budget sets before and after the increase in price in the SAME graph. Let good 1 and good 2 be the horizontal and vertical axis respectively. (c) Observing the price increase, the government considers replacing the food stamp program with an ad valorem food subsidy. In the new subsidy program, the household will get q% of her food expenditure reimbursed. Find out the mini- mum subsidy rate q under which Sally can still afford her initial bundle (300, 12)