First and second ionization enthalpies of lithium are 520 kJ mol$$^{-1}$$ and 7297 kJ mol$$^{-1}$$ respectively. Energy required to convert 3.5 mg lithium (g) into Li$$^{2+}$$(g) [Li(g) $$\to$$ Li$$^{2+}$$(g)] is _______ kJ mol$$^{-1}$$. (nearest integer)
[Molar mass of Li = 7 g mol$$^{-1}$$]