A composite wall is to be constructed of in. of stainless steel (k = 10 Btu/h

A composite wall is to be constructed of ¼ in. of stainless steel (k = 10 Btu/h ft °F), 3 in. of cork board (k = 0.025 Btu/h ft °F), and ½ in. of plastic (k = 1.5 Btu/h ft °F). Determine the thermal resistance of this wall if it is bolted together by ½-in. -diameter bolts on 6-in. centers made of
a. Stainless steel
b. Aluminum (k = 120 Btu/h ft °F)