A manufacturing firm has four 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: Customer (requirement) Factory Customer 1 Customer 2 Customer 3 Customer 4 (capacity) (125) (156) (175) (75) A (166) $15 $16 $26 $17 3 (75) $26 $12 $19 $26 C (166) $22 $26 $25 $14 D (256) $21 $15 $28 $12 How many arcs will the network have?