Using the AASHTO flexible design procedure, design a pavement for a rural interstate highway. The expected design ESAL is 13X 10^6. The pavement structure is to consist of asphalt concrete with an elastic modulus of 400,000 psi, a granular base with an elastic modulus 26,000 psi and granular Sub-base coarse elastic modulus is 12000 ps. The elastic modulus of the subgrade is 8,000 psi. It is estimated that it will take a week for water to drain from the pavement and that the pavement will be saturated about 15% of the time.