Atoms of an unknown element have the following masses and percent abundance: 90.92% of the atoms have a mass of 19.988 u, 0.26% of the atoms have a mass of 20.983 u, and 8.82% of atoms have a mass of 21.978 u.
Calculate the average atomic mass of this element.
20.983 u
20.166 u
25.567 u
19.988 u