In a batch reactor, the gas phase 5A 2B reaction is carried out at constant room temperature. It is known that the reaction has first-order rate kinetics. At constant pressure, the reactor initially contains 75% A, 20% inert, and 5% B by mole. 6 minutes from the start of the reaction. Afterwards, it was observed that the volume of the reaction mixture decreased by 15% compared to the initial volume.

a) Find the reaction rate constant.

b) If only reactant A is fed to the batch reactor with an initial reaction volume of 5L, 10 min.

What will be the volume of the reaction mixture then?