An additional unit of Old Product X will bring Cindy an MU of 15 utils; an additional unit of New Product Y will bring Cindy an MU of 30 utils; and an additional unit of New Product Z will bring Cindy an MU of 40 utils. If a unit of Old Product X costs $10, a until of New Product Y costs $30, and a unit of New Product Z costs $20, which product will Cindy prefer to spend her money on?

a. Old Product X.

b. New Product Y.

c. New Product Z.

d. More information is required.