What would be the net annual cost of the following checking accounts? $($ $ LO$4\mathrm{.}4)$

a$.$ Monthly fee, $$3\mathrm{.}75$; processing fee, $$0\mathrm{.}25$ per check; checks written, an average of $14$ a month.

b$.$ Interest earnings of $4$ percent with a $$500$ minimum balance; average monthly balance, $$600$; monthly service charge of $$15$ for falling below the minimum balance, which occurs three times a year $($no interest earned in these months$).$