Ben's average velocity is determined by dividing the total displacement by the total time taken. In this case, Ben walks 300 m in total (500 m to the store and 200 m past his house). It takes him 17 minutes to leave his house until he stops to talk to his neighbor. Dividing the total displacement of 300 m by the total time taken of 17 minutes, we get an average velocity of approximately 17.6 m/min (rounded to the nearest tenth).