A hot isothermal surface is to be cooled by attaching an array of parallel, equally spaced vertical plates, plates are of equal length and width =352 mm, the film temp -50 °C,Air properties (k = 0.02735 W/m.K, a =2.487E-5 m/s, v=1.798E-5 m/s, Pr=0.7228). What is the plate spacing (mm) that maximizes heat transfer from the array when AT between hot surface and surrounding air is 82°C?