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

b$.$ Interest earnings of $6$ percent with a $$500$ minimum balance; average monthly balance, $$600$; monthly service charge of

$$18$ 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 $