A gas-phase reaction of 5A 2B is being carried out in a batch reactor at a constant temperature under a fixed pressure. It is known that the reaction follows first-order kinetics. At the beginning, the reactor contains 75 mol% A, 20 mol% inert, and 5 mol% B. After 6 minutes from the start of the reaction, it is observed that the reaction mixture has decreased in volume by 15% compared to the initial volume. a) Find the reaction rate constant. b) If only A reactant is fed into the batch reactor with an initial reaction volume of 5L, what will be the volume of the reaction mixture after 10 minutes?