A 4-mm-diameter spherical ball at 50°C is covered by 1-mm-thick plastic insulation (k = 0.13 W/m⋅K). The ball is exposed to a medium at 15°C, with a combined convection and radiation heat transfer coefficient of 20 W/m²⋅K. Determine if the plastic insulation on the ball will help or hurt heat transfer from the ball.

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Plastic insulation 4 mm 1 mm FIGURE P17-93