If element X consists of 64.6% of atoms with a mass of 34.0 u, 18.2% of atoms with a mass of 35.0 u, and 17.2% of atoms with a mass of 36.0 u, what is the average atomic mass of element X to the nearest hundredth?

The mass of 60.4% of the atoms of an element is 68.9257 u. There is only one other natural isotope of that element, and its atomic mass is 70.9249 u. Calculate the average atomic mass of the element. Using the periodic table and/or the table of the elements, write its symbol and name.