Polyvinylchloride automotive body panels (k = 0.092 w/m\u22c5k, cp = 1.05 kj/kg\u22c5k, \u3c1 = 1714 kg/m3), 1-mm thick, emerge from an injection molder at 120oc. they need to be cooled to 40oc by exposing both sides of the panels to 20oc air before they can be handled. if the convective heat transfer coefficient is 15 w/m2\u22c5k and radiation is not considered, the time that the panels must be exposed to air before they can be handled is (a) 0.8 min (b) 1.6 min (c) 2.4 min (d) 3.1 min (e) 5.6 min