Different combination of cylinder are shown in the figure. Select the correct alternatives for the thermal resistance of the following combinations : A thin cylinder of diameter 'd' is surrounded by another cylinder.

Select all that apply

• Option A

  Thermal resistance of '1' combination is $\frac{2l}{5k\pi d^2}$

• Option B

  Thermal resistance of '2’ combination is$\frac{4l}{5kA}$

• Option C

  Thermal resistance of '1' combination is $\frac{5l}{2k\pi d^2}$

• Option D

  Thermal resistance of '2’ combination is

  $\frac{5l}{4kA}$