Answer
See the answer below.
Work Step by Step
From De Broglie's equation:
$\lambda=\frac h{m.v}$
$\lambda=6.626\times20^{-34}\ J.s\times 1\ (kg.m^2/s^2)/J\div (0.046\ kg\times 30\ m/s)$
$\lambda=4.80\times 10^{-34}\ m=4.80\times 10^{-25}\ nm$
For the given wavelength:
$v=6.626\times20^{-34}\ J.s\times 1\ (kg.m^2/s^2)/J\div (0.046\ kg\times 5.6\times10^{-12}\ m)$
$v=2.57\times10^{-21}\ m/s$
