The Mutation Rate of a Gene in a Species of Minnows

Multiple Choice

The mutation rate of a gene in a species of minnows is 2 per million nucleotides per generation.Only 25 percent of the mutations of this gene are selectively neutral; the rest are deleterious.What is the substitution rate of this gene (per million nucleotides per generation) ?

A) 0.25
B) 0.5
C) 2
D) 4
E) This question cannot be answered without information about the size of the minnow population.