(2) base contributions have been paid for the following number of months:(a) one-half of the total number of months included in the contributor’s base contributory period, but not less than 24 months, with respect to the pension referred to in section 106;
(b) one-third of the total number of months included in the contributor’s base contributory period, but not less than 60 months, with respect to the pension referred to in section 106.1;
(c) one-third of the total number of months included in the contributor’s base contributory period, but not less than 36 months, with respect to the benefits referred to in section 107.