A student marks his starting point on a grassy field. He then makes three moves: 20 m east, 40 m north, and 80 m west. Where is his final position relative to his starting point? a 60 m east and 40 m north b 40 m west and 60 m north c 60 m east and 40 m south d 60 m west and 40 m north e 40 m east and 60 m south