Answer
$264m/s$
Work Step by Step
We know that
$mv=\frac{E}{C}$
This can be rearranged as:
$v=\frac{E}{mc}$
We plug in the known values to obtain:
$v=\frac{1}{226.025406u}(\frac{1u}{931.5MeV/c^2})(\frac{0.186MeV}{c})$
$v=8.83\times 10^{-7}c=264m/s$