2. Consider a household iron whose base plate is made from 1.4 kg of aluminium (p= 2702 kg/m, c = 896 J/kgK, k = 240 W/mK) and has a surface area of 0.046 m. Initially, the iron is in thermal equilibrium with the surrounding ambient air at 21C. The iron is then switched on and heat is generated uniformly within the base plate at a rate of 500 W. The convection heat transfer coefficient between the base plate and the air is h.. = 11 W/mK. Determine: (a) The time required for the base plate to reach 140C. [40 marks] (b) The final temperature of the iron if the heating element is left continuously on. [10 marks]