To minimize the company's overall cost per unit, we need to determine which plant should produce each day's orders based on their respective cost functions. We can use a graph to visualize the cost schedule for each plant, where the x-axis represents the number of units produced and the y-axis represents the cost per unit.
We can plot the cost schedules for each plant on the same graph and find the point of intersection where the cost per unit is the same for two plants. At this point, we can choose the plant with the lower cost per unit to produce that day's orders.
If there are three plants, we can repeat this process for all three pairs of plants and find the optimal combination for each day's orders.