Repeat Problem 7.9 if the extrusion cross-section is elliptical, major axis normal to the air flow and same mass per unit length. The major axis of the elliptical cross-section is 5.46 cm and its perimeter is 12.8 cm. From Problem 7.9: A long copper extrusion is removed from a heat-treatment oven at 400?C and immersed into a 50?C air stream flowing at 10 m/s velocity. Due to oxidation, the surface of the copper has an emissivity of 0.9. Determine the time required for the center of the copper to cool to 100?C.GIVENA long elliptical copper extrusion in an air streamInitial temperature (To) = 400?CAir Temperature (T??) = 50?CAir velocity (V??) = 10 m/sSurface emissivity (ε) = 0.9Elliptical cross-section with major axis normal to the air flowLength of the major axis of the ellipse (D) = 5.46 cm = 0.0546 mPerimeter of ellipse (P) = 12.8 cm = 0.128 mSame mass per unit length as Problem 7.9ASSUMPTIONSAir flow is perpendicular to the axis of the extrusionVariation of the copper properties with temperature isnegligible

U= 10 m/s D=5.46 cm T-- 60C