Use data given in the following table to calculate the molar mass of naturaly occuring argon isotopes:
`{:("Isotope",,"Isotopic molar mass",,"Abundance"),(.^(36)Ar,,35.96755 g mol^(-1),,0.337%),(.^(38)Ar,,37.96272 g mol^(-1),,0.063%),(.^(40)Ar,,39.9624 g mol^(-1),,99.600%):}`

Explanation

`"Molar mass of Ar"=Sigmaf_(i)A_(i)`
`" "=0.00337xx35.96755+0.00063xx37.96272+0.99600xx39.96925`
`" "=39.948" g mol"^(-1)`.