Suppose the managers at FedEx Office wish to meet the increasing demand for color photocopies and to have more reliable service. (Refer to Exercise 4-36.) As a goal, they would like to have at least a 99.9% chance of being able to furnish a black-and-white copy or a color copy on demand. They also wish to purchase only four copiers. They have asked for your advice regarding the mix of black-and-white and color copiers. Supply them with your advice. Provide calculations and reasons to support your advice.