A heat exchanger handles \(40 \mathrm{~kg} / \mathrm{min}\) of water which is heated from \(20^{\circ} \mathrm{C}\) to \(70^{\circ} \mathrm{C}\) by a hot gas entering the heat exchanger at \(150^{\circ} \mathrm{C}\) and flow rate \(80 \mathrm{~kg} / \mathrm{min}\).

Determine the change in entropy. Assume specific heat for water as \(4.18 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}\) and for gases as \(1.045 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}\).