Percentage yield and purity

Tin(IV) oxide, SnO₂, is reduced by carbon according to the equation

$SnO_2 + 2C \rightarrow Sn + 2CO$.

If 800 g of an impure sample of SnO₂ produces 96 g of tin, what is the percentage purity of SnO₂ in the sample? (Ar: Sn = 119, O = 16)