A single$-$pass, cross$-$flow heat exchanger uses hot exhaust gases $($mixed$)$ to heat water $($unmixed$)$ from $30$ to $80C$ at a rate of $3k\frac{g}{s}.$ The exhaust gases, having thermophysical properties similar to air, enter and exit the exchanger at $225$ and $100C,$ respectively. If the overall heat transfer coefficient is $160\frac{W}{m^2}*K,$ estimate the required surface area, in $m^2.$

$A=$

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$m^2$