(1) in the case of a pension or annual allowance:(a) either in equal deductions from the monthly payments of pension or annual allowance over a period equal to the fraction of the period referred to in section 31 and for which no payment was made under sections 27 to 29; such deduction shall not exceed 30% of the gross monthly payments;
(b) or, where the beneficiary so elects, by the deduction of a lump sum once the pension or annual allowance becomes payable;