Copper Has an Atomic Weight of 63

Multiple Choice

Copper has an atomic weight of 63.55 u.If 69.17% of Cu exists as Cu-63 (62.93960 u) ,what is the identity and the atomic mass of the other isotope?

A) Cu-64; 63.82 u
B) Cu-64; 64.16 u
C) Cu-65; 64.16 u
D) Cu-65; 64.92 u
E) Cu-66; 65.91 u