A 2 cm thick slab of commercial thermocole, 100 cm² in cross-section and having thermal conductivity 2 x 10^-4 cal sec^-1 cm^-1 (C^o)^-1 has insulating regions differing by 100°C.
The quantity of heat flowing through it in a day will be:

• A

  20.4 kcal

• B

  43.2 kcal

• C

  86.4 kcal

• D

  63.6 kcal