Question: International Waste Deposits, Inc. has applied to the country government for permit to construct a toxic waste disposal facility. Trucks carrying toxic waste to the proposed site must go under an overpass on interstate 80, or must exit the freeway and detour through the center of a business district. Managers are worried about possible health effects in case of an accident. The overpass has a clearance of 23 feet. The height of the trucks that carry the toxic waste has a mean of 18 feet and standard deviation of three feet.

A. Find the proportion of trucks carrying toxic wastes that must take the detour through the center of the business district.

B. Find the height of a new overpass structure that would be required to accommodate 99.9% of the trucks.