A wall is constructed of a section of stainless steel [k = 16 W/m C] 4.0

Question:

A wall is constructed of a section of stainless steel [k = 16 W/m ∙ ºC] 4.0 mm thick with identical layers of plastic on both sides of the steel. The overall heat-transfer coefficient, considering convection on both sides of the plastic, is 120 W/m2 ∙ ºC. If the overall temperature difference across the arrangement is 60ºC, calculate the temperature difference across the stainless steel.