Consider a windshield of length L = 800 mm and thickness t = 6 mm and driving conditions for which the vehicle moves at a velocity of V = 70 mph in ambient air at T[infinity], o = −15°C. From laboratory experiments performed on a model of the vehicle, the average convection coefficient on the outer surface of the windshield is known to be correlated by an expression of the form ¯¯¯¯¯ Nu L = 0.030 Re 0.8 L Pr 1 / 3 Nu¯L=0.030 ReL0.8Pr1/3 , where ReL ≡ VL/v. Air properties may be approximated as k = 0.023 W/m ⋅ K, v = 12.5 × 10−6 m2/s, and Pr = 0.71. If Tdp = 10°C and T[infinity], i = 50°C, what is the smallest value of ¯ h i h¯i required to prevent condensation on the inner surface?