Let MUa = z = 10 - x and MUb = z = 21 - 2y, where z is marginal utility per dollar measured in utils, x is the amount spent on productA, and y is the amount spent on product B. Assume that the consumer has $10 to spend on A and B--that is, x + y = 10. How is the $10 best allocared between A abd B? how much utility will the marginal dollar yield?