A manufacturing firm has three plants and wants to find the most efficient means of meeting the requirements of its four customers. The relevant information for the plants and customers, along with shipping costs in dollars per unit, are shown in the table below: a. Which of the following is an objective function for the problem? b. Which of the following is a constraint for the customers? c. This model indicates that it costs ___ dollars to ship one unit from plant(s) _ to customer(s) d. At the optimal solution, how many units would be received by customer 3 from plants 1,2 and 3 ? e. At the optimal solution, what is the minimum total cost to meet all customer requirements