What is the Staffel A that has a Staffel D of Energie Cottbus and a Staffel C of Chemie Leipzig and a Staffel B of 1. FC Union Berlin?
CREATE TABLE "1971_1984" (
  "season" text,
  "staffel_a" text,
  "staffel_b" text,
  "staffel_c" text,
  "staffel_d" text,
  "staffel_e" text
);
SELECT "staffel_a" FROM "1971_1984" WHERE "staffel_d"='energie cottbus' AND "staffel_c"='chemie leipzig' AND "staffel_b"='1. fc union berlin';