(1) For the purposes of this Act -
(a) a person shall be deemed to be over any age therein mentioned if he has attained that age and shall be deemed to be under any age therein mentioned if he has not attained that age;
(b) a person shall be deemed to be between two ages therein mentioned if he has attained the first-mentioned age but has not attained the second-mentioned age;
(c) a person shall be deemed not to have attained the age of 16 years until the commencement of the 16th anniversary of the day of his birth, and similarly with respect to any other age;
(d) regulations may provide that, for the purpose of determining whether a contribution is payable in respect of any person, or at what rate a contribution is payable, that person shall be treated as having attained at the beginning of a contribution week, or as not having attained until the end of a contribution week, any age which he attains during the course of that week;
(e) the circumstances in which a person is to be r