<p>The atomic masses of He and Ne are 4 and 20 a.m.u., respectively. The value of the de Broglie waelength of He gas at&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mo>-</mo><msup><mn>73</mn><mo>&#8728;</mo></msup><mi>C</mi></math>&nbsp;is&nbsp; &quot;M&quot; times that of the de Broglie wavelength of Ne at&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mn>727</mn><mo>&#8728;</mo></msup><mi>C</mi></math>&nbsp;. M is:</p>