MTC (MegaTelCo) has decided to use supervised learning to address its problem of churn in its wireless phone business. As a consultant to MTC, you realize that a main task in the business understanding/data understanding phases of the data mining process is to define the target variable. In one or two sentences, please suggest a definition for the target variable. Be as precise as possible- someone else will be implementing your suggestion. (Remember: it should make sense from a business point of view, and it should be reasonable that MTC would have data available to know the value of the target variable for historical customers.)