Any town or city which claims that its equalized valuation of the property relieved from taxation by “An Act imposing a business profits tax, repealing certain taxes, providing transitional measures, revising the rate of certain taxes, and providing for return of revenue to cities and towns” enacted by the 1970 special session of the general court, for the years 1966, 1967, 1968, and 1969 increased by an average of more than 10 percent, may apply to the tax commission for a certificate to that effect. After such investigation and hearing as the tax commission may require, which shall be conducted at the expense of the applicant, the commission shall, if it finds the application to have merit, certify to the state treasurer the average percentage rate of increase of equalized valuation of said property in said years. The state treasurer shall determine the amount of revenue returnable to the applicant in 1970 by increasing the amount certified to him under N.H. Rev. Stat. § 31-A:2 by the percentage certified to him by the tax commission under this section.