A new building to be located in a cold climate is being designed with a basement that has an L=200 mm thick wall. Inner and outer basement wall temperatures are t=20 c and t=0 c respectively. the architect can specify the wall material to be either aerated concrete block with k= 0.15 W/m.K or stone mix concrete. To reduce the conduction heat flux through the stone mix wall to a level equivalent to that of the aerated concrete wall, what thickness of extruded polystyrene sheet must be applied onto the inner surface of the stone mix concrete wall? Floor dimensions of the basement are 20 m * 30 m, and the expected rental rate is $50/m2/month. What is the yearly cost,in the terms of lost rental income, if the stone mix concrete wall with polystyrene insulation is specified?