Question

a. a biologist needs to determine the number of possible arrangements of 4 kinds of molecules in a chain. if the chain contains 8 molecules with 2 of each kind how many different arrangements are possible? (permutations/combinations) answer:2520
b. trish has a penny, 3 nickels, 4 dimes, and 3 quarters in her pocket. How many different arrangements are possible if she removes one coin at a time from her pocket? (permutations/combinations) answer:46200

I don't really know which formula to use if its combo or perm