Instruct: On what date was the tournament played that eneded with a winning score of +6 (74-71-70-71=286) and margin of victory of 2 strokes, and with Arnold palmer as the runner-up?
Output: SELECT Date FROM table WHERE Runner(s)-up = arnold palmer AND Margin of victory = 2 strokes AND Winning score = +6 (74-71-70-71=286)