If the price in dollars of a stereo system is given by p(q)= (7600/q^2) +1000, where q represents the demand for the product, find the marginal revenue when the demand is 20.

To find the marginal revenue, we need to take the derivative of the price function with respect to q:

p'(q) = -15200/q^3

Then, we can substitute q=20:

p'(20) = -15200/20^3 = -19

Therefore, the marginal revenue when the demand is 20 is -$19.