(1) The contribution conditions for State pension (contributory) are -

(a) subject to subsection (3), that the claimant has entered into insurance at least 10 years before attaining pensionable age or deferred pensionable age, as the case may be,

(b) that the claimant-

(i) has qualifying contributions in respect of at least 520 contribution weeks, or

(ii) in the case of a person who on or before 6 April 1997, is a voluntary contributor paying contributions under Chapter 4 of Part 2, has an aggregate of qualifying contributions and voluntary contributions in respect of 520 contribution weeks, of which not less than 156 are qualifying contributions, or

(iii) in any other case, has an aggregate of qualifying contributions and voluntary contributions in respect of 520 contribution weeks of which not less than 260 are qualifying contributions,

since his or her entry into insurance,

(c) subject to subsection (6D), that the claimant has a yearly average or, in the case of a person who attains pensionable age on or after 6 April 1992, an alternative yearly average of not less than 48.