If when the resolution, provided for in Section 45-37-72.21, is adopted, a countywide election is scheduled to be held not less than three weeks and not more than eight weeks from the date on which the resolution provides the first election shall be held, to fill the vacancy, the runoff election, if necessary, shall be held on the date on which the countywide election is scheduled to be held. If when the resolution, provided for in Section 45-37-72.21, is adopted, there is no countywide election scheduled to be held not less than three weeks and not more than eight weeks from the date on which the resolution provides for the first election to be held, the resolution shall provide for the runoff election, if any runoff election is necessary to be held three weeks subsequent to the date on which the first election shall be held to fill the vacancy.