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 product A, 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 allocated between A and B? How much utility will the marginal dollar yield?