Name the least episode for fibre cement siding
CREATE TABLE "season_18_2011_2012" (
  "series_ep" text,
  "episode" real,
  "segment_a" text,
  "segment_b" text,
  "segment_c" text,
  "segment_d" text
);
SELECT MIN("episode") FROM "season_18_2011_2012" WHERE "segment_d"='Fibre Cement Siding';