How to make a nested if function in harlowe twine 2.0

I was trying to make a rank up system in my game where with every certain number of wins players will rank up to the next rank I was able to make a variable and a simple if function as so: (if: $rankearned < 20)["C-Class"] (else:)["B-Class"] but I don't know how to add an A-Class after 30 more wins and a S-Class after 50 more wins can you guys help me