Section 11. On or before the first day of June of each year, each city and town having twenty thousand or more residents on its numbered resident list shall submit to the office of jury commissioner an automated copy of such list. Such automated copy, hereinafter in this chapter referred to as the ''numbered resident file'', shall be a data processing file contained on a magnetic computer tape or disk of such kind and in such format as shall be specified in the regulations of the jury commissioner. Any city or town having less than twenty thousand residents on its numbered resident list may comply with this section. Any city or town that complies with this section shall have fulfilled all of its obligations for submission of population data to the office of jury commissioner for the current year. The cost of preparing the numbered resident file shall be paid by the city or town. The office of jury commissioner shall return said computer tapes to the cities and towns within a reasonable time.