Answer
See explanation below.
Work Step by Step
a.The percentage of sulfur-32 atoms is 95.02%, this is same as the relative abundanceof 32S.
b.As per the problem, sulfur-32 is the lightest isotope and this means other 5% sulfur atoms are heavier than sulfur-32.This makes the average mass of all sulfur atoms greater than mass of sulfur-32 atom.