A hot, freshly-sterilised fermentation medium is cooled in a double-pipe heat-exchanger. The medium enters the inner pipe of the exchanger at $95^{\circ} \mathrm{C}$ and leaves the exchanger at $40^{\circ} \mathrm{C}$. Cooling water, flowing counter-currently to the medium, enters the annulus of the exchanger at $15^{\circ} \mathrm{C}$ and leaves the exchanger at $45^{\circ} \mathrm{C}$. The overall heat transfer coefficient is $1350 \mathrm{~W} \mathrm{~m}^{-2}\: ^{\circ} \mathrm{C}^{-1}$. The rate of heat transfer per unit area will be $\_\_\_\_\_$ $\mathrm{W} / \mathrm{m}^{2}$.
(Round off to the nearest integer)
