You have been asked to design pavement an access highway to a major truck terminal. the design daily truck traffic consists of the following: 80 single axles at 22,500 lb each, 570 tandem axles at 25,000 lb each, 50 tandem axles at 39,000 lb each, and 80 triple axles at 48,000 lb each. the highway is to be desigend with rigid pavement having a modulus of rupture of 600 lb/in^2 and a modulus of elasticity of 5 million lb/in^2. the reliability is to be 95%, the overall standard deviation is 0.4, the drainage coefficient is 0.9, delta PSI is 1.7 ( with TSI of 2.5), and the load transfer coefficient is 3.2. the modulus of subgrade reaction is 200 lb/in^3. if a 20-year design life is to be used, determine the required slab thickness.