CREATE TABLE table_53971 ("Res." TEXT, "Record" TEXT, "Opponent" TEXT, "Method" TEXT, "Event" TEXT, "Round" FLOAT, "Time" TEXT, "Location" TEXT)

How long is the ko (punch) fight against scott smith?
SELECT "Time" FROM table_53971 WHERE "Method" = 'ko (punch)' AND "Opponent" = 'scott smith'
SELECT "Time" FROM "table_53971" WHERE "Method" = 'ko (punch)' AND "Opponent" = 'scott smith'