8. A PFR operating isothermally at 773 K is used to conduct the following elementary reaction: A →＞ B+ C. If a feed of pure A enters at 5 atm and at a flow rate of 0.193 f'/s, what length of pipe with a cross-sectional area of 0.0388 f is necessary for the reaction to achieve 90% conversion? Data: & = 7.80 x 10' exp[-19,200/T] sl.