An insulating foam board must limit the energy conduction rate to no more than 500W across an area of 1.6m2 when a 15∘C temperature difference is applied. If the foam’s thermal conductivity is 1.4Wm−1K−1, what minimum thickness should the board have?
a) 0.042m
b) 0.0067m
c) 0.067m
d) 1.29m