Section 21.05 - Calculation of the Assessment(1) For metered end suppliers, the Assessment shall be calculated by multiplying the Withdrawal Amount by the Assessment Rate.(2) For unmetered end suppliers the Assessment shall be calculated as follows: (a) for unmetered end suppliers which serve a population of 900 persons or more, by multiplying the Estimated Withdrawal Amount by the Assessment Rate;(b) for unmetered end suppliers which serve a population of less than 900 persons, the Assessment shall equal a flat rate set by the Department, in consultation with the advisory committee, for the following categories based on the population served by the system.1. Suppliers serving 25-100 persons2. Suppliers serving 101-200 persons3. Suppliers serving 201-899 persons(3) The Department shall encourage universal master metering in order to accurately quantify the amount of water which passes through each distribution system and to fairly apportion the assessment among users.