Allozyme phenotypes of alcohol dehydrogenase in the flowering plant Phox drummondii are determined by three co-dominant alleles of a single gene. In one sample of 70 plants the following data were obtained:

Genotype A1A1 A2A2 A3A3 A1A2 A1A3 A2A3
Number 4 24 10 10 2 20
What is the frequency of the A2 allele in this sample?

0.628

0.238

0.557

0.432

0.337