What is the total number of Pick, when Position is OT, when Overall is greater than 91, when Round is greater than 21, and when College is Mississippi?
CREATE TABLE "washington_redskins_draft_history" (
  "round" real,
  "pick" real,
  "overall" real,
  "name" text,
  "position" text,
  "college" text
);
SELECT COUNT("pick") FROM "washington_redskins_draft_history" WHERE "position"='ot' AND "overall">91 AND "round">21 AND "college"='mississippi';