The intensity of solar radiation at the top of Mercury's atmosphere is about 9080 W/m². Calculate the average energy density u of the solar radiation incident on Mercury. a) 1.816 x 10¹⁰ J/m³ b) 4.54 x 10⁹ J/m³ c) 9.08 x 10⁹ J/m³ d) 3.632 x 10¹0 J/m³