Answer
The coefficient of kinetic friction between the surface of the hill and the toboggan is $0.14$
Work Step by Step
As shown in the image below, the force that propels the toboggan to run downhill is $m\vec{g}\sin\theta$, with $\theta$ to be the angle of the hill.
Opposing this movement is the kinetic frictional force $f_k$. Since the toboggan is in constant velocity, these 2 forces balance each other. $$mg\sin\theta=f_k=\mu_kF_N$$
The normal force $F_N$ is in opposite direction with $mg\cos\theta$. Since these two forces do not affect the movement, they balance each other, too. $$F_N=mg\cos\theta$$
Therefore, $$mg\sin\theta=\mu_k\times mg\cos\theta$$ $$\sin\theta=\mu_k\cos\theta$$ $$\mu_k=\tan\theta=\tan8^o=0.14$$
