Probability problem: can anyone check my answers for this?
wayne has 1 ten-dollar bill, 2 five-dollar bills, and 5 one-dollar bills in his wallet.

a) wayne randomly chooses a bill from his wallet, puts it back, then picks another bill, and puts that one back, too. what is the probability that both were five-dollar bills?
would the answer for this be 4/16 or 1/4?

b) wayne randomly pulls out a bill from his wallet, and then, without putting it back, randomly pulls a second bill from his wallet. he then puts both bills back into the wallet. what is the probability that both of the bills pulled out were five-dollar bills?
would the answer for this be 2/8*1/7 = 1/28?
if i'm wrong correct me!