A stoichiometric mixture of fluorine and nitrogen (containing a small amount of argon) is fed to process producing nitrogen trifluoride (NF3). The incoming process feed is combined with a recycle stream (see below) and fed to the process reactor. Fifteen percent of the fluorine and nitrogen that enter the reactor are converted to NF3. The reactor output is fed to a condenser where all of the NF3 condenses. Most of the unreacted gases leaving the condenser are fed back to the reactor. Because argon will accumulate to unacceptable levels if 100% of the unreacted gases are recycled, a small fraction of the unreacted gas stream leaving the condenser is taken out of the process as a "bleed stream". An analysis of the feed to the process gives 0.285 moles of argon in100 moles of original process feed.

a) What fraction of the unreacted gas leaving the condenser must be bled off to keep the amount of argon entering the reactor no higher than 0.5 mol%?