#### Answer

(a) 10 m/s
(b) A slowed down, C sped up, B had a constant speed

#### Work Step by Step

(a) Because the starting and ending values on the graph are the same for all three winners, their average speed (rate of change) will be the same:
$\displaystyle \frac{d(10)-d(0)}{10-0}=\frac{100-0}{10}=10$ m/s
(b) Although their average speeds were the same, the three skiers had different speeds throughout the race. Skier A started fast, but then slowed down. Skier C started slow, but then sped up (accelerated). Skier B maintained a constant speed (equal to the average speed of 10 m/s).