“…In Figure 6, customers 4 and 1 of route 1, customers 3 and 6 of route 2, and customers 2 and 5 of route 3 need to be paired. Consequently, the list is: [ [4,3], [4,6], [4,2], [4,5], [1,3], [1,6], [1,2], [1,5], [3,2], [3,5], [6,2], [6,5]], a total of [(3 − 1)ˆ2 + (3 − 1)] × 2 = 12 pairs.…”