Using the equation v(avg)=distance/time and the equation v=v(original)+a(t) solve for acceleration 2600=0+a(12) a=216.66666 m/s^2
Then, you use the equation v^2=v(original)+2a*(change in x) 2600^2=2(216.666666)*change in x 6760000/2/216.666666 = 15600 meters which is the length of the race