If, during the period beginning when the need for an electoral redistribution arises under section 37 , 38 or 39 and ending when the electoral redistribution becomes final, the need for another electoral redistribution arises under any of those sections (including the same section)—
(a) the need for the other electoral redistribution does not arise; and
(b) for the purposes of any later application of section 39 , any month occurring wholly or partly during the period is to be disregarded.