fluids class

A 3-ft-diameter duct is used to carry ventilating air (p = 2.373 x 10- slugs/ft. = 1.57 x 10-4 ft/s) into a vehicular tunnel at a rate of 12000 ft/min. Tests show that the pressure drop is 1.4 in. of water per 1500 ft of duct. What is (a) the value of the friction factor for this duct and (b) the approximate size of the equivalent roughness of the surface of the duct? Use this figure