Plans described
A defined benefit plan is described in this clause if—
(I)#
the plan provides benefits to a closed class of participants,
(II)#
for the plan year as of which the class closes and the 2 succeeding plan years, the plan satisfies the requirements of section 410(b) and subsection (a)(4) (without regard to this subparagraph but taking into account the rules of subparagraph (I)),
(III)#
after the date as of which the class was closed, any plan amendment which modifies the closed class or the benefits provided to such closed class does not discriminate significantly in favor of highly compensated employees, and
(IV)#
the class was closed before April 5, 2017 , or the plan is described in subparagraph (C).