What is the location of the match with chad armstrong as the opponent?
CREATE TABLE "mixed_martial_arts_record" (
  "res" text,
  "record" text,
  "opponent" text,
  "method" text,
  "event" text,
  "round" real,
  "time" text,
  "location" text
);
SELECT "location" FROM "mixed_martial_arts_record" WHERE "opponent"='chad armstrong';