please help!

A composite wall has been constructed sandwiching a 50mm layer of insulation between two metal sheets. Thermal conductivity of insulation material is 0.046W/m. C. Each metal sheet has a thickness of 3mm and their thermal conductivity is 60W/m. C. If the wall separates refrigerated air at 4C from ambient air at 25C, what is the heat transfer rate per unit area? Natural convection heat transfer coefficients at the inner and outer surfaces may be taken as 5W/m2.C. (20 points) State all assumptions you make. ( 5 points)