Casper consumes Goods x and y. Good x is sold at a price of $2 per unit. Good y is sold at a price of $3 per unit. Casper's income is 20 dollars and his utility function is U(x, y) = x + 3y. a. (1 pt) Sketch Casper's budget line. b. (1 pt) Sketch some of his indifference curves and label the point that he chooses as the optimal bundle. c. (2 pts) Calculate the amount of each good Casper demands at these prices and this income. d. (2 pts) Given the price of Good x at $2 per unit, for what prices of y will Casper changes his demand?