A monopoly is considering selling several units of a homogeneous product as a single package. A typical consumer's demand for the product isQ^d= 130 -0.25P, and the marginal cost of production is $160.

a. Determine the optimal number of units to put in a package. 90 units

b. How much should the firm charge for this package? $16200

I know A is correct but B isn't. I could use some help in answering B.