(a) Effective as of October 1, 1974, female policemen shall make the same contributions for survivors’ annuities or other benefits as are in effect for male policemen, to the end that no distinction or difference shall exist as between male and female policemen with respect to rates of contribution or other provisions of this Article.
     (b) Any female policeman shall have the option of making contributions for the aforesaid purposes, covering the period prior to October 1, 1974, and receiving pension credits therefor including concurrent credits from city contributions. Such contributions shall include interest at 4% per annum from the dates such contributions should have been made from the beginning of their service to the dates of payment to the end that equal pension credits for survivors’ benefits may be provided for all policemen under this Article.