Use the following information to answer the questions below.
Skin color in a certain species of fish is inherited via a single gene with four different alleles.
-One fish of this type has alleles 1 and 3 (S₁S₃)and its mate has alleles 2 and 4 (S₂S₄). If each allele confers a unit of color darkness such that S₁ has one unit, S₂ has two units, and so on, then what proportion of their offspring would be expected to have five units of color?