A cross$-$flow heat exchanger $($radiator$)$is used to cool a coolant which leaves an engine manifold

at $105$oC $($Cp$=3800$J$.$kg$-1$K$-1).$A fan draws ambient air $($Cp$=1005$J$.$kg$-1$K$-1)$at $20$oC through the heat

exchanger at a rate of $1\mathrm{.}0$kg$.$s$-1,$while a pump circulates the coolant at a rate of $1\mathrm{.}0$kg$.$s$-1.$Both flows

are unmixed. Reference to heat exchanger performance data indicates that a UA value of $1000$W$.$K$-1$

may be assumed for these conditions. Determine the coolant outlet temperature from the heat

exchanger.