7. In paragraph 4(b) above, the gross equivalent annual percentage rate means a rate calculated in the same manner as the net annual percentage rate but with the amount of any payment to be made by the authority to the lender increased by the product of the formula—
where
“z” is so much of the amount of the payment as is in respect of interest; and
“y” is the basic rate of income tax as at the relevant date expressed as a percentage.