For the purpose of computing the tax payable under this Part by an individual for a taxation year, there may be deducted the amount determined by the formula A × B where A is the appropriate percentage for the taxation year; and B is the amount determined by the formula C - D where C is the total of all amounts each of which is the portion of the cost of an eligible public transit pass or of an eligible electronic payment card, attributable to the use of public commuter transit services in the taxation year and before July 2017 by the individual or by a person who is in the taxation year a qualifying relation of the individual, and D is the total of all amounts each of which is the amount of a reimbursement, allowance or any other form of assistance that any person is or was entitled to receive in respect of an amount included in computing the value of C (other than an amount that is included in computing the income for any taxation year of that person and that is not deductible in computing the taxable income of that person).