What is the average rank for USA when the market value is 407.2 billion?
CREATE TABLE "2011_list" (
  "rank" real,
  "company" text,
  "headquarters" text,
  "industry" text,
  "sales_billion" real,
  "profits_billion" real,
  "assets_billion" real,
  "market_value_billion" real
);
SELECT AVG("rank") FROM "2011_list" WHERE "headquarters"='usa' AND "market_value_billion">407.2;