A credit shall be allowed against the primary tax imposed by this article, which shall be the research and development credit as provided in sections three and three-b, article thirteen-d of this chapter for taxable years beginning after December 31, 1988: Provided, That the amount of this credit may not reduce by more than fifty percent the amount of the net tax liability of the taxpayer for the taxable year: Provided, however, That one-tenth of the entire amount of the eligible investment, upon which the credit is predicated pursuant to sections three and three-b, article thirteen-d of this chapter, taken as a deduction in determining its federal taxable income for the taxable year shall be an adjustment increasing federal taxable income under section six of this article: Provided further, That the taxpayer may at its option elect in lieu of claiming the credit allowable by this section to not increase its federal taxable income under section six of this article and thereby take as a full deduction under this article for the taxable year the amount of its eligible investment in research and development for the taxable year, which was taken as a deduction as a deduction on its federal return for such taxable year.