If a person who, immediately before the date of assuming office as the Chairperson or a Member was in receipt of or being eligible so to do, has opted to draw, a pension, other than a disability or wound pension, in respect of any previous service under the Central Government, his salary in respect of service as the Chairperson or a Member shall be reduced--
         (a) by the amount of that pension; and
         (b) if he had, before assuming office, received, in lieu of a portion of the pension due to him in respect of such previous service, the commuted value thereof, by the amount of that portion of the pension.