After receiving the engineer's report, the commission shall study the preliminary plat and other material for conformity thereof to these regulations. The commission may confer with the subdivider on changes deemed advisable and the kind and extent of such improvements to be made by the subdivider. The commission shall approve or reject such plat within forty five (45) days after the date of submission thereof to the commission. If the commission does not act within forty five (45) days, the preliminary plat shall be deemed to be approved; provided, however, that the subdivider may agree to an extension of the time for a period not to exceed sixty (60) days. The approval of the preliminary plat by the commission shall be null and void unless the final plat is presented to the commission within one hundred eighty (180) days after date of approval. (2000 Code § 176.14)