At the plant of a bearing manufacturer, 2 cm steel balls are quenched in an oil bath from an initial temperature of 800 F. The oil flows past the suspended balls at a mean velocity of 5 ft/s and an average temperature of 60 F. Estimate the time required for the ball to cool to 200 F. The oil has the following properties: lbm p=52 ft3 Btu = 0.54 Cp k = 0.071 Btu lbm OF lbm'ft of = = 0.00083 lbm ftis The steel has the following properties: p = 491 km, Cp ft3' Btu = 0.107 Ibm F