A call center of a major furniture and appliance retailer takes calls from customers to provide after-sales service. The retailer must ensure that exactly one operator is present to receive calls between 8:00 a.m. and 10:00 p.m. each day of the week. There are four operators who work part-time for the retailer and whose availabilities for each day of the week (i.e., the maximum number of hours of work that the operator is willing to offer) are presented in the table below. In this table, days 1,2,3,4 and 5 correspond to Monday, Tuesday, Wednesday, Thursday and Friday respectively. The hourly wage for telephone operators is also shown in the table. This varies depending on the person's experience. The retailer must also ensure a minimum of working hours each week for each operator, 8 hours per week for operators 1 and 2 and 6 hours per week for operators 3 and 4 . The retailer's goal is to allocate a number of working hours for each operator so as to cover the 14 hours of activity each day of the week while minimizing costs. 1. Formulate this problem using a linear programming model. Do not forget to provide an interpretation of the decision variables, the objective and the constraints