A hypothetical element has two main isotopes

Question

with mass numbers of 71 and 74. If 80.00% of
the isotopes have a mass number of 71 amu,
what atomic weight should be listed on the
periodic table for this element?
(answer in AMU).

Answer 1

I would rather see the atomic weight of each isotope; failing that I'm assuming they are 71 and 74.
0.80(71) + 0.20(74) = ?

Answer 2

71.6