CREATE TABLE table_71539 ("Place" TEXT, "Player" TEXT, "Country" TEXT, "Score" TEXT, "To par" TEXT, "Earnings  (  $  ) " FLOAT)

What is the average earnings of a United States player who had a score of 72-68-74-72=286?
SELECT AVG("Earnings ( $ )") FROM table_71539 WHERE "Country" = 'united states' AND "Score" = '72-68-74-72=286'
SELECT AVG("Earnings ( $ )") FROM "table_71539" WHERE "Country" = 'united states' AND "Score" = '72-68-74-72=286'