Assume that the estimated equivalent annual departures in terms of B-757 as design aircraft with maximum gross take-off weight of 225,000 lb for a transport airport is calculated to be 3000 per year. If the modulus of subgrade reaction for the runway section of the airfield is 50 pci, determine the required minimum thickness of PCC slab (with flexural strength of 700 psi) that will be placed on top of a prepared base course of a rigid pavement structure for the runway at this airfield. Assume that the estimated equivalent annual departures in terms of B-757 as design aircraft with maximum gross take-off weight of 225,000 lb for a transport airport is calculated to be 3000 per year. If the modulus of subgrade reaction for the runway section of the airfield is 50 pci, determine the required minimum thickness of PCC slab (with flexural strength of 700 psi) that will be placed on top of a prepared base course of a rigid pavement structure for the runway at this airfield