A physical quantity $\overrightarrow S is defined as \overrightarrow S = (\overrightarrow E \times \overrightarrow B )/{\mu _0}, where \overrightarrow E is electric field, \overrightarrow B is magnetic field and \mu
0
is the permeability of free space. The dimensions of \overrightarrow S $ are the same as the dimensions of which of the following quantity(ies)?