The amount of radiant energy emitted by a surface is given by the equation where q repre...

The amount of radiant energy emitted by a surface is given by the equation where q represents the rate of thermal energy, per unit time, emitted by the surface in watts; ε is the emissivity of the surface 0< ε<1 and is unitless; σ is the Stefan-Boltzman constant (σ = 5.67×10^-8); A represents the area of the surface in m²; and T_S is the surface temperature of the object expressed in Kelvin. What is the appropriate unit for σ, if the above equation is to be homogeneous in units?