Two insulating materials of thermal conductivity 'Ic' and '2 k' are available for lagging a pipe carrying a hot fluid. If the radial thickness of each material is the same, then— (a) Material with...

Two insulating materials of thermal conductivity 'Ic' and '2 k' are available for lagging a pipe carrying a hot fluid. If the radial thickness of each material is the same, then—

(a) Material with higher thermal conductivity should be used for the inner layer and one with lower thermal conductivity for the outer.

(b) Materials with lower thermal conductivity should be used for the inner layer and one with high thermal conductivity for the outer.

(c) It is immaterial in which sequence the insulating materials are used.

(d) It is not possible to judge unless numerical values of materials are given.