Question

a football coach starts at the 50-yard line Smiley: Angel and walks to the 10-yard line (B) . He turns around and walks to the 40-yard line Smiley: Coffee Cup . HE turns around again and walks back to the 0-yard line (D). He turns around once more and walks back to the 30-yard line Smiley: E Mail , thus completing his ten minutes of pacing. The coach's average velocity is___.