3) A 2.5-mm-diameter electrical wire at 60C is covered by 3-mm-thick plastic insulation (k=0.17 W/mK). The wire is exposed to a medium at 50C, with a convection heat transfer coefficient of 22W/m2K. (a) Determine the rate of heat transfer (15 points). (b) Determine the heat transfer rate if the thickness of this plastic insulation doubles (10 points)