Calculate the average implicit interest rate on the following non-interest-bearing accounts:

a. A $1 million account with average management costs of $150 000 and fees earned of $35 000

b. A $150 000 account with average management costs of $25 000 and fees earned of $5000 c. A $1000 account with average management costs of $1000 and fees earned of $750 d. Which account is least costly for the DI that carries these accounts?