There are two naturally occurring isotopes of Gallium, $69$Ga$,$ with a mass of $68\mathrm{.}92558$ amu and $71$Ga with a mass of $70\mathrm{.}92470$ amu. If $69$Ga has an abundance of $53\mathrm{.}220$ percent, what is the average atomic weight of Gallium?

Antimony has two naturally occurring isotopes: one with a mass of $120\mathrm{.}90382$ amu and another with a mass of $122\mathrm{.}90422$ amu. In a strange sample, you find that the lighter isotope makes up $52\mathrm{.}115\%$ of the antimony present. What is the average atomic weight of antimony based on this sample?