Please help with homework Moby-Dick: What use does Melville make of the qualities of three mates

What use does Melville make of the qualities of three mates, the prudent Starbuck, the indifferent Stubb, and the mediocre Flask – and the three harpooners? What is the function of the minor characters, such as Elijah, Fedallah, or Pip? One traditional method of Biblical interpretation looked at texts in fourfold ways, namely, the literal, moral, allegorical, and anagogical. First, the literal or historical: consider Moby-Dick as documentary, its scientific center in cetology, its study of an actual whale incident, its placing the whale in context in marine biology.