Question

Antti entered a $10$-kilometer race. His goal is to finish in one hour. He starts off sprinting, and completes the first $2$ kilometers of the race at an average speed of $12$ kilometers per hour.

To achieve his goal of a one-hour finish time, what average speed must Antti maintain for the last $8$ kilometers of the race?

Enter your answer as a number in decimal form, without units.