(a) The surviving spouse, the dependent child or children or dependent parent or parents of any employee who has lost or shall lose his or her life by reason of injury, illness or disease resulting from an occupational risk or hazard inherent in or peculiar to the service required of employees while the employee was engaged in the performance of his or her duties as an employee of the agency, or the survivor of a retirant who dies from any cause after having been retired pursuant to the provisions of section nine of this article, is entitled to receive and shall be paid from the fund benefits as follows: To the surviving spouse annually, in equal monthly installments during his or her lifetime, one or the other of two amounts, which shall become payable the first day of the month following the employee's or retirant's death and which shall be the greater of:
(1) An amount equal to nine-tenths of the base salary received in the preceding full twelve-month employment period by the deceased employee: Provided, That if the employee had not been employed with the agency for twelve full months prior to his or her death, the amount of monthly salary shall be annualized for the purpose of determining the benefit; or