Rank the following gases in order of decreasing rate of effusion.? ar c_3h_8 he

According to the Graham's law, effusion rate is inversely proportional to the molecular weight. It means that the gas with the lowest molecular weight will have the highest effusion rate.
The moleclar weights of these gases are as follows:
Ar = 40 gm/mol
C_3H_8 = 3x12+8= 44 gm/mol 
He = 4 gm/mol
 So, the order according to decreasing rate of effusion will be:
1. He 
2. Ar
3. C_3H_8