Water flowing at $70 \mathrm{~kg} / \mathrm{min}$ is heated from $25^{\circ} \mathrm{C}$ to $65^{\circ} \mathrm{C}$ in a counter-flow double pipe heat exchanger using hot oil. The oil enters at $110^{\circ} \mathrm{C}$ and exits at $65^{\circ} \mathrm{C}$. If the overall heat transfer coefficient is $300 \mathrm{~W} /\left(\mathrm{m}^{2} \mathrm{~K}\right)$, the heat exchanger area is $\_\_\_\_
\_ \: \mathrm{m}^{2}$ (rounded off to $1$ decimal place).
GIVEN: Specific heat of water and oil are $4.2 \mathrm{~kJ} \: /\left(\mathrm{kg}\: { }^{\circ} \mathrm{C}\right)$ and $2 \mathrm{~kJ} /\left(\mathrm{kg}{ }^{\circ} \mathrm{C}\right)$, respectively.
