(a)
Any employee—
(1)
who is placed as a result of reduction-in-force procedures from a position subject to this subchapter to another position which is subject to this subchapter and which is in a lower grade than the previous position, and
(2)
who has served for 52 consecutive weeks or more in one or more positions subject to this subchapter at a grade or grades higher than that of the new position,
is entitled, to the extent provided in subsection (c) of this section, to have the grade of the position held immediately before such placement be considered to be the retained grade of the employee in any position he holds for the 2-year period beginning on the date of such placement.