The going rate for lessons varies depending on your location, your level of experience, and in some cases, your instrument. Take a look at profiles of other teachers in your area to get an idea of what teachers with similar qualifications to yours are charging.
You can experiment with your rate until you accept your first student. After that, your rate will be locked in for the remainder of the year. Contact the TMT administration before Nov. 1st if you would like to change your rates for the following year.