Answer
See the explanation
Work Step by Step
a.
From the graph we can see that $B$ reached $500$ meter before $A$ did, thus $B$ won the race.
b.
For $A$, from $d=0$ to $d=200$ at $t=0$ to $t=10$,
Average speed is
$\dfrac{200-0}{10-0}=20\frac{m}{s}$.
For $B$, from $d=0$ to $d=100$ at $t=0$ to $t=10$,
Average speed is
$\dfrac{100-0}{10-0}=10\frac{m}{s}$
c.
For $A$, from $d=400$ to $d=500$ at $t=25$ to $t=40$,
Average speed is
$\dfrac{500-400}{40-25}\approx 6.67\frac{m}{s}$
For $B$, from $d=200$ to $d=500$ at $t=20$ to $t=35$,
Average speed is
$\dfrac{500-200}{35-20}=20\frac{m}{s}$
