Consider a 1000-W iron whose base plate is made of .5 cm thick aluminium alloy 2024-T6 (p = 2270 kg/m^3, cp= 875 J/kg*K, alpha = 7.3 x 10 ^-5 m^2/s). The base plate has a surface area of .03 m^2. Initially, the iron is in thermal equilibrium with the ambient air at 22 degrees C. Taking the heat transfer coefficient at the surface of the base plate to be 12 W/m^2*K and assuming 85% of the heat generated in the resistance wires is transferred to the plate, determine how long it will take for the plate temperature to reach 140 degrees C. Is it realistic to assume the plate temperature to be uniform at all times?