A $50$ mm $*45$ mm $*20$ mm cell phone charger $($the shape of the charger is a rectangular parallelepiped$)$ has a constant surface temperature when plugged into an electrical wall outlet. The surface of the charger is subject to a free convection heat transfer coefficient of $h=4\mathrm{.}5\frac{W}{m^{2.}}K$ with the room air having a temperature of $15C.$ By assuming steady conditions and neglecting radiation, if the electric power of the charger is $0\mathrm{.}487$ W $,$ the surface temperature of the charger is:

a$.28\mathrm{.}04C$

b$.27\mathrm{.}16C$

c$.38\mathrm{.}04C$

d$.26\mathrm{.}11C$