CREATE TABLE table_4528 ("Name" TEXT, "Pole Position" TEXT, "Fastest Lap" TEXT, "Winning driver" TEXT, "Winning team" TEXT, "Report" TEXT)

Who had the fastest lap when Al Unser won?
SELECT "Fastest Lap" FROM table_4528 WHERE "Winning driver" = 'al unser'
SELECT "Fastest Lap" FROM "table_4528" WHERE "Winning driver" = 'al unser'