(e)
For the purposes of determining the eligibility of a member for a bonus under this section and of computing the amount of that bonus—
(1)
any period of enlistment (including any extension of an enlistment)
(A)
that is incurred by the member for the purpose of continuing to qualify for continuous submarine duty incentive pay under section
301c of this title, and
(B)
for which no bonus is otherwise payable; or
(2)
any unserved period of two years or less of an extension of an enlistment for which no bonus has been paid or for which no bonus is otherwise payable under this section,
may, under regulations prescribed by the Secretary concerned, be considered as part of an immediately subsequent term of reenlistment (or as part of an immediately subsequent voluntary extension of an enlistment).