Suppose the demand function for a certain product is given by q = f(p) = 10900e-0.21p a) Find the number of products sold when the price of the product is $6. (Round your answer to the nearest whole number.) Number of products sold: b) Find a formula for the rate of change in the number of products sold when the price is p dollars. f' (p) = c) What is the rate of change in the number of products sold when the price is $6? (Round your answer to one decimal place.)