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 (in kilometers per hour) must Antti maintain for the last $8$ kilometers of the race? Enter your answer as a number in decimal form, without units.