Suppose a new species of shark is discovered, and the dorsal fin length is found to be determined by additive alleles at three independently assorting loci (A, B, and C). The dorsal fin length of aabbcc sharks is 12 cm, and the dorsal fin length of AABBCC sharks is 30 cm. Assuming that the alleles contribute equally, what will be the length (in cm) of the dorsal fin of an animal with genotype AAbbcc