An element found in another galaxy exists as two isotopes. If 80.0% of the atoms have an atomic mass of 80.00 atomic mass units and the other 20.0% have an atomic mass of 82.00 atomic mass units, what...

An element found in another galaxy exists as two isotopes. If 80.0% of the atoms have an atomic mass of 80.00 atomic mass units and the other 20.0% have an atomic mass of 82.00 atomic mass units, what is the approximate atomic mass of the element?

(a) 80.4 amu

(b) 81.0 amu