Section 9(b) in The Madurai City Municipal Corporation Service Rules, 1981
(b)Promotion Category 3(a) and category 3(b) shall be from the category 3(c) and category 3(d). Common seniority shall be maintained between the categories 3(a) and 3(b). Likewise, common seniority shall be maintained between the categories 3(c) and 3(d):
