What is the net annual cost of the following chequing accounts?

a$.$ Monthly fee, $$3\mathrm{.}60$; processing fee, $50$ cents per cheque; cheques written, an average of $2$ a month; $$1\mathrm{.}00$ per debit transaction over the $20$ debit transactions per month that are free with an average of $40$ per month made. $($Round your final answer to $2$ decimal places. Omit the $"$$$"$ sign in your response.$)$

Annual cost

$ $$ b$.$ Interest earnings of $4$ percent with a $$500$ minimum balance; average monthly balance, $$700$; monthly service charge of $$20$ for falling below the minimum balance, which occurs three times a year $($no interest earned in these months$).($Round your final answer to $2$ decimal places. Omit the $"$$$"$ sign in your response.$)$

Net cost

$$