Discover how atomic mass is calculated. 1. We saw previously that the average atomic mass of boron is 10.81 amu. In the simulation, select boron. Next, click "My Mix" to create your own mixture of boron isotopes. Begin by adding a single Boron-10 isotope to the mix. How many Boron-11 isotopes must you add to bring the average atomic mass up to the known atomic mass of boron, 10.81 amu? Hint: Add Boron-11 isotopes until the atomic mass reads 10.81 amu. 1 3 4 11 I