(a)such number of office of Sabhapati and Up-Sabhapati of Gram Panchayat in each district for the Scheduled Castes and the Scheduled Tribes and the number of such offices shall bear as nearly as may be, the same proportion to the total number of offices in the district as the population of the Scheduled Castes and of the Schedule Tribes in the district bears to the total population of the district.