Ak = wv, for a

pls answer!

Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

Suppose that the price p (in dollars) and the weekly sales x (in thousands of units) of a certain commodity satisfy the demand equation 4p cubedplusx squaredequals38 comma 400. determine the rate at which sales are changing at a time when xequals80, pequals20, and the price is falling at the rate of $.20 per week.

Can some one me with these questions