Hello, i need help with this chemical engineering problem. Please i need every step explained for the resolution of the exercise.

The reaction in the elementary gas phase A+B+C+D takes place in a plug flow reactor at constant pressure and temperature with a conversion of A by 50%. The reactor is fed with an equimolecular mixture of A and B.

a) Define and solve the design equation for the plug flow reactor.

b) It is proposed to add a second perfect mix reactor (CSTR) upstream of the PFR. The CSTR reactor has the same volume as the PFR. Determine the output conversion from the CSTR and PFR. The flow rate and input variables remain the same as with a single PFR.