For purposes of determining the federal income tax liability of a taxpayer subject to Rhode Island income tax, the Rhode Island income of the taxpayer under § 44-30-12 and § 44-30-16 shall be determined by excluding any income, gain, or preference items resulting from the sale, transfer, or exercise of qualified and nonqualified stock options, the stock issued or transferred on the exercise of any option, and warrants issued with respect to options and/or stock, of a qualifying corporation; provided, that the taxpayer was a qualifying taxpayer and the taxpayer’s employer who issued the option was a qualifying corporation at the time the taxpayer acquired a vested interest in the option and exercised the option.