Using the information in the table to the right, calculate the average atomic mass of strontium. Report to two decimal places. amu A 3 column table with 4 rows titled Strontium. Column 1 is labeled Isotope with entries Upper S r-84, Upper S r-86, Upper S r-87, Upper S r-88. Column 2 is labeled Mass (a m u) with entries 83.913428, 85.909273, 86.908902, 87.905625. Column 3 is labeled Abundance (percent) with entries 0.56, 9.86, 7, 82.58.