Calculate the number of hydrogen and carbon present in 4g of methane

I'm going to do it by stoichiometry :

molar mass of CH4 is 16

and there are 4 H atoms in each CH4 so one mole CH4 consists of 4 x 6.022x10^23 H atoms

so :

4gr CH4 x (1mole CH4 /16 gr CH4) x (4 x 6.022 x 10^23 H atoms/1mole CH4) =

=6.022 x 10^23 H atoms

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.