Lena is comparing offers from two banks on checking accounts that include debit cards. Bank A charges $20 monthly fee for a checking account and debit card, with unlimited transactions. Bank B charged a $5 monthly fee for a checking account and debit card, plus $ 0.50 for each transaction.
Suppose Lena makes 35 transactions in a given month.

How much would she pay at each bank for the given month?
Bank A
Bank B

For the given month, which bank is cheaper and by how much?
Bank A. is cheaper than Bank B by $
or
Bank B is cheaper than Bank A by $