Nellie works for a large manufacturing company. she heads the information systems department and works closely with the accounting department. nellie knows a lot about the company's database systems and accounting practices. her responsibilities include working with the company's vendors to create data communication lines. the company works with many vendors, including a large number of new vendors that have been added due to the company's rapid growth. recently, nellie has become concerned about the effectiveness of the internal controls in ensuring the integrity of the purchasing function. she expressed her concerns to senior management and has been asked to recommend proactive steps the company can take to prevent fraud from collusion between employees and vendors. what would you recomend?