B 
$A$, $B$ and $C$ start from the same place at the same time and chase a cyclist in front of them along the same road. The three cars catch up with him in $6$, $10$ and $12$ minutes respectively. Given that car $A$\textquotesingle s speed is $24$ kilometers per hour, car $B$\textquotesingle s speed is $20$ kilometers per hour. Find car $C$\textquotesingle s speed. 
(a) $$21$$ 
(b) $$19$$ 
(c) $$18$$ 
(d) $$16$$ 
(e) $$15$$ 