A house wall may be approximated as two 1.2-cm layers of fiber insulating board, an 8.0-cm layer

Question:

A house wall may be approximated as two 1.2-cm layers of fiber insulating board, an 8.0-cm layer of loosely packed asbestos, and a 10-cm layer of common brick. Assuming convection heat-transfer coefficients of 12 W/m2 ∙ ºC on both sides of the wall, calculate the overall heat transfer coefficient for this arrangement.