At what gas temperature trms would the root-mean-square (rms) speed of a helium atom be equal to that of an oxygen molecule in a gas at 300 k?

The rms speed of a gas is given by
(1)
where
R is the gas constant
T is the absolute temperature of the gas
is the molar mass of the gas

For the oxygen molecules in the problem, T=300 K, and the molar mass of molecular oxygen is , therefore the rms speed of the molecules is


We want the atoms of helium to have the same rms speed. So we can re-arrange equation (1), and using  and  (molar mass of helium) in order to find the helium atom temperature T:

Ithink the answer is c. make unnecessarily  wide gestures