Answer
$\mu_k=0.61 N$
Work Step by Step
Force of friction and normal reaction are mutually related as follows:
$f=\mu_k F_N$
where $\mu_K$ is coefficient of kinetic friction
We also know that $F_N=mg$ (weight of the baseball player )
Hence $f=\mu_kmg$ or $\mu_k=\frac{f}{mg}$
Substituting the values and solving:
$\mu_k=\frac{470}{(79)(9.8)}$
$\mu_k=0.61 N$
