question

An industrial wall is constructed of 20cm thick fireclay of thermal conductivity 1W/mC. This is covered on the outer surface with a 3cm layer of insulating material of thermal conductivity 0.075W/mC. The innermost surface is at 940C and the outermost surface is at 40C. The steady state of heat transfer is occurring through the wall. So what is the rate of heat transfer rate that is occurring through the wall? What is the temp of the interface of these walls