Comparing Cost of Checking Cost: What would be the net annual cost of the following checking accounts?

a) Monthly fee, $3.75; processing fee, $0.25 cent per check; check written, an average of 22 a month

b) Interest earning of 6 percent with a $500 minimum balance; average monthly balance, $600; monthly services charge of $15 for falling below the minimum balance, which occurs three times a year (no interest earned in these months.)