Heat transfer

A wooden wall in a house is 2dm thick and =0.14W/(m*K). The generating heat was enough to reach a temperature of 15^oC inside the house, while the outside temperature is -20^oC.

The heat transfer coefficient on the inside and outside the wall is 10 W/m²K.

How much thicker must the wall be to reach a temperature of 21^oC inside the house?

Hint: Heat loss through other surfaces in the house is the same as for the wooden wall