Two insulating materials of thermal conductivity K and 2K are available for lagging a pipe carrying a hot fluid. If the radial thickness of each material is same
(a) Material with high thermal conductivity should be used for inner layer and one with lower thermal conductivity for the outer.
(b) Material with lower thermal conductivity should be used for inner layer and one with higher thermal conductivity for the outer
(c) It is immaterial in which sequence the insulating material are used
(d) It is not possible to judge unless numerical values of dimensions are given