A Naturally Occurring Element Consists of Two Isotopes

Multiple Choice

A naturally occurring element consists of two isotopes. Calculate the fractional abundances for the two isotopes, if its average atomic mass is 107.87 u.
Isotope 1: 106.91 u ---- %
Isotope 2: 108.90 u ----- % ,Hint: Set up a weighted average calculation where one percentage is x and the other percentage is (100-x) .

A) 106.91 u, 39.264 %; 108.90 u, 60.736 %
B) 106.91 u, 44.150 %; 108.90 u, 55.850 %
C) 106.91 u, 55.850 %; 108.90 u, 44.150 %
D) 106.91 u, 51.759 %; 108.90 u, 48.241 %
E) 106.91 u, 41.759 %; 108.90 u, 58.241 %