A Gene Family Has Been Accumulating Nucleotide Substitutions at a Rate

Multiple Choice

A gene family has been accumulating nucleotide substitutions at a rate of 0.25 per million years.On average, there have been 80 substitutions between the common ancestor of this gene family and each of the various living forms of this gene.How many substitutions are expected to have evolved between any pair of living forms of genes from this gene family?

A) 20
B) 40
C) 80
D) 160
E) 320