I assume that you had sent of plea of non guilty...
Before the trial, pursuant to article 166.2 of the Code of Penal Procedure, you may change your plea of not guilty and enter a plea of guilty. The fee for a change of plea are 25$
Cost for a judgment rendered during a contested trial : 80$
Please note that if you do not send the full amount payable with your change of plea, you will be required to pay an additionnal fee of 7$ for sending a notice of judgment and for non-payment of the fine and costs with the transmission of your plea of guilty.