(e) [FN1] In special cases, where back licenses fees have accumulated so as to work an extreme hardship on the applicant, the Department may allow the applicant to pay on back license fees on an installment plan. In no case may the current license fee be paid in this manner. The payments of the back fees shall be made at the discretion of the Department to fit the individual case. A license issued under such conditions shall be revoked for non: payment [FN2] of any part of the fees.