A concrete wall \(20 \mathrm{~cm}\) thick is initially at a temperature of \(20^{\circ} \mathrm{C}\), and is exposed to steam at pressure \(1 \mathrm{~atm}\) on both sides. Find the time for the system to reach a nearly steady state. Find the rates of condensation of steam at various values of time.

The thermal diffusivity constant for concrete is needed. Use a value of \(7.5 \times 10^{-7} \mathrm{~m}^{2} / \mathrm{s}\).