All requirements for the degree shall be completed in not more than six calendar years, including leaves of absences, for those who start the program with an M.S. degree in the same field, and not more than eight calendar years, including leaves of absences, for those who start the program with only a B.S. degree. If the M.S. degree is in an unrelated field, the time limit shall be eight years. Meritorious cases, however, may be given extensions not exceeding one year at a time but in no case totaling more than five calendar years, including leaves of absence, provided the student is required to take three additional units of graduate courses for every two years or fraction thereof of extension.