(a) the greater ofi. the difference between 60% of the amount of the contributor’s retirement pension, calculated in accordance with section 135, and 40% of the amount of the surviving spouse’s retirement pension, and
ii. 37.5% of the amount of the contributor’s retirement pension calculated in accordance with section 135;
(b) the difference betweeni. 1/12 of 25% of the amount of the average of the Maximum Pensionable Earnings for the year in which the surviving spouse reaches 65 years of age and for each of the two preceding years, and
ii. the amount of the retirement pension of the surviving spouse.