A/ W The marginal cost (in dollars per square foot) of installing x square feet of kitchen countertop is given by C'(x) = x" a) Find the cost of installing 50 ft of countertop. b) Find the cost of installing an extra 16 ft of countertop after 50 ft2 have already been installed. a) Set up the integral for the cost of installing 50 ft of countertop. C(50) = dx