A long hexagonal copper extrusion is removed from a heat-treatment oven at 400?C and immersed into a 50?C air stream flowing perpendicular to its axis at 10 m/s. Due to oxidation, the surface of the copper has an emissivity of 0.9. The rod is 3 cm across opposing flats, has a cross-sectional area of 7.79 cm2, and a perimeter of 10.4 cm. Determine the time required for the center of the copper to cool to 100?C.GIVENA long hexagonal copper extrusion in an air stream flowing perpendicular to its axisInitial temperature (To) = 400?CAir temperature (T??) = 50?CAir velocity (V??) = 10 m/sSurface emissivity (ε) = 0.9Distance across the flats (D) = 3 cm = 0.03 mCross sectional area of the extrusion (Ac) = 7.79 cm2 = 7.79 x 10??4 m2Perimeter of the extrusion (P) = 10.4 cm = 0.104 mASSUMPTIONSVariations of the copper properties with temperature arenegligible

D-3 cm Alr U= 10 m/s T.- 50C