What is the least clock speed (MHz) with January 1986 as introduced?
CREATE TABLE "list_of_macintosh_models_grouped_by_cpu_" (
  "processor" text,
  "model" text,
  "clock_speed_m_hz" real,
  "l1_cache_bytes" text,
  "introduced" text,
  "discontinued" text
);
SELECT MIN("clock_speed_m_hz") FROM "list_of_macintosh_models_grouped_by_cpu_" WHERE "introduced"='january 1986';