Hot exhaust gases are used in a shell-and-tube exchanger to heat \(3.0 \mathrm{~kg} / \mathrm{s}\) of water from 30 to \(90^{\circ} \mathrm{C}\). The gases, assumed to have the properties of air, enter at \(210^{\circ} \mathrm{C}\) and leave at \(105^{\circ} \mathrm{C}\). The overall heat transfer coefficient is \(175 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}\). Using the effectivenessNTU method, calculate the area of the heat exchanger.