The elementary gas-phase reaction A B takes place isobarically and isothermally in a PFR where 63.2% conversion is achieved. The feed is pure A. It is proposed to put a CSTR of equal volume upstream of the PFR. Based on the entering molar flow rate to A to the first reactor, what will be exit conversion from the PFR, X2, based on the feed to first reactor? The entering flow rates and all other variables remain the