Chemistry -Periodic Trends?

Element Q has three isotopes. The first has a m of 83.9114 amu and makes up 21.15% of a standard sample. The second isotope has a m of 85.4615 amu and makes up 68.00% of a standard sample. The third isotope has a m of 86.7279 amu and makes up the remainder of a standard sample. What is the average atomic m of this element