Which constructor makes the ej15 ej15b chassis?
CREATE TABLE "drivers_and_constructors" (
  "entrant" text,
  "constructor" text,
  "chassis" text,
  "engine" text,
  "tyre" text,
  "driver" text,
  "rounds" text
);
SELECT "constructor" FROM "drivers_and_constructors" WHERE "chassis"='ej15 ej15b';