A fly with a mass of $1.0 \times 10^{-4} \mathrm{kg}$ crawls across a table at a speed of $2 \mathrm{mm} / \mathrm{s} .$ Compute the de Broglie wavelength of the fly and compare it with the size of a proton (about $\left.1 \mathrm{fm}, 1 \mathrm{fm}=10^{-15} \mathrm{m}\right)$.