Question $2$: You are supposed to order a double$-$wall glass window for your new lab. The doublewall is $0\mathrm{.}7-$m$-$high and $1\mathrm{.}5-$m$-$wide and it consists of two $4-$mm$-$thick layers of glass $)=(0\mathrm{.}78\frac{W}{m}*C$ which is separated by stagnant air space $)=(0\mathrm{.}026\frac{W}{m}*C.$ The desired maximum heat loss is $70W$ where the inner surface should be at $20C$ while the outer surface is at $-15C.$ Please determine the thickness of the stagnant air space needed to not lose more than $70W$ of heat. The convection heat transfer coefficients on the inner and outer surfaces of the window are as follows: $h_1=10\frac{W}{m^2},C$ and $h_2=40\frac{W}{m^2}*C.$ Please draw a sketch for the question. $($Assume steady$-$state heat transfer and please ignore radiation$).$