What is the length of the track named michigan international speedway?
CREATE TABLE "isc_tracks" (
  "track_name" text,
  "location" text,
  "length" text,
  "seating" real,
  "year_opened" real,
  "year_acquired_a" real
);
SELECT "length" FROM "isc_tracks" WHERE "track_name"='Michigan International Speedway';