A proportional relationships constraint would be O guaranteeing that a certain amount of workforce will be available for a certain month O ensuring that the budget allocated to sales is twice that of research and development o balancing the input to the output during production O making certain that only a certain amount of units are produced Solve the problem Going-Mail is a fright company that recently made a study on its customer satisfaction. The results show that most customers dissatisfied from using Going-Mail because of personnels' lack of courtesy. To address this, Going-Mail provided special training to its employees in customer service. The decision to train the Going-Mail is the result of: O association O reduction cause and effect modeling classification