Problem #$4(5$ points$)$

Air is to be heated steadily by an $8-kW$ electric heater as it flows through an insulated duct. If the aif enters at $50C$ at a rate of $2k\frac{g}{s},$ the exit temperature of the air is:

$($a$)46\mathrm{.}0C$

$($b$)50\mathrm{.}0C$

$($c$)54\mathrm{.}0C$

$($d$)55\mathrm{.}4C$

$($c$)58\mathrm{.}0C$