Answer
$4.7\times10^{-12}m$
Work Step by Step
We find the wavelength using equation 27–8. The neutron is not relativistic.
$$\lambda=\frac{h}{p}=\frac{h}{mv}$$
$$\lambda=\frac{6.63\times10^{-34}J \cdot s }{(1.67\times10^{-27}kg)(8.5\times10^4m/s)}$$
$$=4.7\times10^{-12}m$$
