Helium versus R134a refrigerant gas

Anyone know how to calculate what the equivalent of 5 Grams/per annum of R134a gas is in Helium. I am testing leak rates using a gas mixture of Helium 20% Nitogen 80% at 40 Bars pressure.I am told that 2.5 x 10E-05 is equal to 5 Grams R134a/Annum is this correct and how is it worked out? :?:

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