(a) A protest in writing, under oath, may be filed with the city clerk by a registered elector, not later than 20 days after the city clerk has issued an initial determination of sufficiency, setting forth with particularity the grounds of such protest and the names protested. No such protest shall be accepted by the city clerk until an initial determination of sufficiency has been issued. The city clerk shall mail a copy of such protest to the petition representatives and/or to the protest representatives, together with a notice fixing a time for hearing such protest not less than ten nor more than 20 days after such notice is mailed.