“(3) C is the lesser of the percentage corresponding to the value C would have in the formula in subsection 2 of section 225.2 of the Excise Tax Act, determined for the taxation year, for the financial institution as regards Québec, and the percentage corresponding to the value that same C would have, for the financial institution as regards Québec, determined for the preceding taxation year, if each of those values were determined in accordance with the regulations made under that Act for the purposes of subsection 2.1 of section 228 of that Act and if Québec were a participating province within the meaning of subsection 1 of section 123 of that Act.”