"Suppose that you own a caf and you currently sell 18 cups of premium latte per day. The neighbourhood, where your store is located, has an average daily income of 50 per person. Then a huge international business consultancy constructs a new office building across the street to your caf. The average daily income in the neighbourhood changes to 138 and you note that your sales decreased to 82 cups of premium latte per day." a) Calculate the income elasticity of demand for cups of premium latte. b) Is premium coffee a normal, inferior, or luxury good?