A 70-year-old patient complains of inability to take food, a cosmetic and phonetic defect due to the complete loss of mandibular teeth. Objectively: the lateral segment of the alveolar process of the mandible is significantly atrophied, while the frontal segment is relatively preserved. Buccal folds are attached at the crest of the alveolar process. These clinical presentations correspond with the following class of edentulous jaws according to Keller classification: