Calculate the wavelength of a helium atom whose speed is equal to root mean square speed at 293 K $(rms = \sqrt{3RT/m})$

Question

$(a)\;3.68\times10^{-5}nm\qquad(b)\;7.38\times10^{-5}nm\qquad(c)\;7.38\times10^{-3}nm\qquad(d)\;6.35\times10^{-5}nm$