Answer: 6.
Explanation:
Since it starts with 2 kilometers in 3 minutes add 3 more minutes that would but six then double the kilometers to 4 then add another 3 minutes which would but 9 where it stops and add another 2 in the kilometers then i would be 6 .
step by step:
1. 3 minutes and 2 km
2. add 3 more (6) and double the kilometers 2 times(4)
3. add 3 more (9) and add another 2 to the km (9)