In general
Gross income shall not include so much of any monthly annuity payment under a qualified employer retirement plan as does not exceed the amount obtained by dividing—
(I)#
the investment in the contract (as of the annuity starting date), by
(II)#
the number of anticipated payments determined under the table contained in clause (iii) (or, in the case of a contract to which subsection (c)(3)(B) applies, the number of monthly annuity payments under such contract).