Effusion rate 1.4 times faster SO2(g)

How do I solve this-
Which diatomic gas would effuse at a rate that is 1.4 times faster than the rate at which so2(g) effuses at any given temperature? This is high school chemistry.


I did: (using graham's law) 1.4= sqroot of 64g*mol-1 / xg*mol-1 => 1.96= 64/x => 1.96x=64 => x=32.65g/mol. 32.65/2 (bc its a diatom) => 16.325g/mol which is close to oxygen. 
At first, I found Urms of SO2 using 273k for T, 0.064kg for M and 8.314 for R, I got 326. Then multiplied that by 1.4 and got 456. Then I put 456/326= sqroot of 64g*mol-1/ xg*mol-1 and solved for x. I realized the 456/326 equaled 1.4, so I figured I didn't need to find Urms in the first place.


