Question 2
$A$, $B$ and $C$ run a 200-m race in constant speeds. When $A$ finishes the race, $B$ is 40 m behind $A$ and $C$ is 10 m behind $B$. When $B$ finishes, $C$ still has to run another 2 seconds. How many seconds does $B$ still have to run when $A$ finishes?