. "For the purpose of computing the tax payable under this part for a taxation year, clause 1 of the bill notes that there may be deducted an amount determined by the formula A x B, where A is the appropriate percentage for the year, which is the tax rate in the lowest tax bracket in this Province which is 7.7 per cent, and B is an amount that is deducted in computing the taxpayer's income for the ye" . . . .