How several amino acid differences

Q. Fibrinopeptides (proteins involved in the blood clotting, among other functions) are called to have high amino acid substation rates. Suppose that the average per amino acid site substitution rate in mammalian fibrinogen b (roughly 600 amino acids long) is one substitution every 10 million years. If humans and shrews shared the common ancestor roughly 80 million years ago, ignoring multiple substitutions at the same site, how several amino acid differences have to be expecting to see between a human and shrew Fibrinogen B sequence?

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