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.