If the legislature, having rejected a measure submitted to it by initiative petition, proposes a different measure dealing with the same subject, the secretary of state shall give that measure the same number as that borne by the initiative measure followed by the letter "B." Such measure so designated as "Alternative Measure No. . . . . B," together with the ballot title thereof, when ascertained, shall be certified by the secretary of state to the county auditors for printing on the ballots for submission to the voters for their approval or rejection in like manner as initiative measures for submission to the people are certified.