F5 Physics Temperature

The walls of a container used for keeping objects cool consist of two thickness of wood 0.5cm thick separated by a space 1 cm wide packed with a poorly conducting material. Calculate the rate of flow of heat per unit area into the container if the temperature difference between the internal and external surfaces is 20°C.
(Given that thermal conductivity of wood = 0.24Wm^-1K^-1 and
thermal conductivity of poorly conducting material = 0.024Wm^-1K-1)

Give a me a guide. Thank you.