A sphere, a cube and a thin circular plate are made of same substance and all have same mass. These are heated to 200^oC and then placed in a room. Then the 

$\frac{\mathrm{dT}}{\mathrm{dt}}=\frac{\mathrm{eA\sigma }}{\mathrm{mc}}\left({\mathrm{T}}^4-{\mathrm{T}}_0^4\right)=\frac{\mathrm{eA\sigma }}{\mathrm{V\rho c}}\left({\mathrm{T}}^4-{\mathrm{T}}_0^4\right)$

$\therefore$ Rate of cooling $\mathrm{R}\propto \mathrm{A}$
(As masses are equal, volume of each body must be equal because material is same)
i.e., rate of cooling depends on the area of cross section and we know that for a given volume the area of cross section will be minimum for sphere. It means the rate of cooling will be minimum in case of sphere.
So the temperature of sphere drops to room temperature at last.