Find the de Broglie $ \lambda$ of a neutron, in thermal equilibrium with matter, having an average $KE\: of \bigg(\large\frac{3}{2} \bigg)\: kT$ at $300 \: K.$

Question

$\begin {array} {1 1} (a)\;14.6 \times 10^{-10}m & \quad (b)\;0.146\: nm \\ (c)\;14.6\: nm & \quad (d)\;1.46 × 10^{-9}m \end {array}$