Arefrigerated food warehouse is insulated with a layer of urea-formaldehyde foam 16 in, thick. there is some residual formaldehyde in the foam and it has a concentration of 0.07 lb formaldehyde/ft3 of foam when the material is manufactured. formaldehyde can diffuse into the air where workers will be exposed to the vapor. the outside of the foam is covered with an impermeable layer to prevent moisture migration, so the formaldehyde can only diffuse in one direction, which is into the warehouse. there is a system available that will remove 0.5 lb/hr of formaldehyde from the air during recirculation through the refrigeration system. it will return the air to the warehouse with essentially no formaldehyde, and you can assume the concentration of formaldehyde to be zero in the warehouse as long as the removal system is not overloaded. the warehouse has 33,000 ft2 of insulated surface and the effective diffusivity of formaldehyde through the foam is 1.5e-8 ft2/sec. (a) when the removal system can keep the air free of formaldehyde, determine the concentration of formaldehyde in the foam at the outer surface (next to air). (b) if the penetration distance is defined as the distance from the outer surface of the foam to the position where the concentration has changed by 1.0% from the initial concentration, determine the penetration distance for the foam after2,000,000.0sec.