Thereupon the city or town council shall set a date for hearing any protests against the proposed assessment roll and shall cause a notice of the time and place of the hearing to be published once a week for two successive weeks in the official newspaper of the city or town, the date of the hearing to be not less than thirty days from the date of the first publication of the notice. At the hearing or at any adjournment thereof the council by ordinance shall assess the cost of constructing the sidewalk against the abutting property in accordance with the benefits thereto.