In this subtitle, “employer” also means an employing unit that:
(1) is a nonprofit organization under Section 501(c)(3), Internal Revenue Code of 1986 (26 U.S.C. § 501(c)(3));
(2) is exempt from income tax under Section 501(a), Internal Revenue Code of 1986 (26 U.S.C. § 501(a)); and
(3) employed at least four individuals in employment for a portion of at least one day during 20 or more different calendar weeks during the current year or during the preceding calendar year.