Answer the following question

L' Scenario 174 Assume that a local bank sells two services, chequing accounts and ATM card services. Mr. Leung is willing to pay $10 a month for the bank to service his chequing account and $6 a month for unlimited use of his ATM card. Ms. Gardner is willing to pay only $6 for a chequing account but is willing to pay $10 for unlimited use of herAT M card. Assume that each customer uses only one service and that the bank can provide each of these services at zero marginal cost. Refer to Scenario 17-4. If the bank is unable to use tying, what is the prot- maximizing price to charge for unlimited use of anATM card