After fixing a date for a public hearing pursuant to section 20e, the township board shall direct that the assessment authorized by section 20b be prepared by the township supervisor, who shall levy the total sum estimated of fire protection benefit apportioned in accordance with benefits against all of the property located within the special assessment district benefited by the fire protection water service. The township supervisor shall then report the assessment to the township board. The report shall be made before the date of the hearing.