13. The atomic masses and the natural abundances of the two naturally occurring isotopes of lithium are shown in the table below . Lithium Isotopes Isotope Atomic Mass Natural Abundance %) Li-6 6.02 7.5 Li-77.02 92.5 Which numerical setup can be used to determine the atomic mass of lithium? A (0.075)(6.02u) + (0.925)(7.02u) B) (0.925)(6.02u) + (0.075)(7.02u) C) (7.5)(6.02u) + (92.5)(7.02u) D) (92.5)(6.02u) + (7.5)(7.02u)