A Consumer Consumes Two Normal Goods, Sandwiches and Milk

A consumer consumes two normal goods, sandwiches and milk. When the price of milk is $0.50 per glass, the consumer purchases 40 glasses. When the price rises to $0.65 per glass, the consumer purchases 30 glasses. We can use the information provided by the consumer's optimum choices to derive the

A) demand curve for milk.
B) demand curve for sandwiches.
C) supply curve for milk.
D) labor-leisure tradeoff.