15. Where upon issue of a licence bearing one or more of classes 1 to 5 and one or more of classes 6A, 6B and 6C, the insurance contribution exigible is the amount obtained by adjusting, in accordance with section 45, the sum of contributions as follows:(1) that calculated in accordance with section 13;
(2) that calculated by adding together the insurance contributions for the months, including parts of months, during which the holder is authorized to drive, except for the last month. The insurance contribution for a month corresponds to the percentage, as determined under section 14, of an amount equivalent to the annual insurance contribution set under section 12, before adjustment under section 45, for the holder of a licence bearing one or more of classes 6A, 6B or 6C with no demerit point on record, according to the year of licence issue.