Heavier aircraft require runways with thicker pavement for landings and takeoffs. A pavement 6 inches thick can accommodate an aircraft weighing 80,000 pounds, whereas a 12-inch-thick pavement is necessary for a 350,000-pound plane. The relation between pavement thickness / in inches and gross weight Win thousands of pounds can be modeled by W = Ca^t.

(a) Find values for C and a. 

(b) What is the weight of the heaviest airplane a 9-inch-thick runway can accommodate? 

(c) What is the minimum thickness for a 242,000- pound plane?