A wall 0.7 ft. thick is to be built of a material with a thermal conductivity OF 0.82 Btu/hr-ft-F. The wall is to be insulated with a material having a thermal conductivity of 0.22 Btu/hr-ft-F so that the heat loss per square foot of the wall won't be greater than 600 Btu/hr. If the inside and outside temperatures of the composite wall are 2000 F and 70 F, what's the required thickness of the insulation?
A. 6.00 in. B. 6.24 in. C. 6.55 in. D. 6.85 in.
