Hi, <br/><br/> Which of the following is correct? 'Instruction and Operation' is one category. <br/><br/> '...certain revenue is used in the Instruction and Operation and Infrastructure formulas.' <br/><br/> '...certain revenue is used in the Instruction and Operation, and Infrastructure formulas.' <br/><br/> Is it personal preference? It seems to help clarify the sentence but comes off as awkward. <br/><br/> Thanks for any help.