The gas phase reaction 2A ⇋ B is carried out in an isothermal plug flow reactor. The feed consists of 80 mole % A and 20 mole % inerts. If the conversion of A at the reactor exit is 50%, then $$\frac{{{{\text{C}}_{\text{A}}}}}{{{{\text{C}}_{{{\text{A}}_{\text{0}}}}}}}$$  at the outlet of the reactor is

Correct Answer: $$\frac{5}{8}$$