An element has three isotopes. The masses and % abundances for the isotopes are: Isotope #1 mass 38.96 amu, % abundance=93.26%, Isotope #2 mass 39.96 amu, % abundance 0.012 %, and Isotope #3 mass= 40.96 amu, % abundance=6.73 %. The average atomic mass for this element has to be