Tell me the constructor for alberto colombo and chassis of a1
CREATE TABLE "drivers_and_constructors" (
  "entrant" text,
  "constructor" text,
  "chassis" text,
  "engine" text,
  "tyres" text,
  "driver" text,
  "rounds" text
);
SELECT "constructor" FROM "drivers_and_constructors" WHERE "driver"='alberto colombo' AND "chassis"='a1';