1. Polyvinylchloride automotive body panels (k = 0.092 W/m.K, cp = 1.05 kJ/kg.K, ρ = 1,714 kg/m3), 3-mm thick, emerge from an injection molder at 120C. They need to be cooled to 40C by exposing both sides of the panels to 20C air before they can be handled. If the convective heat transfer coefficient is 30 W/m2.K and radiation is not considered, how long does it take before the panel can be handled?