An insurance firm has five salespeople that they want to assign to five sales regions. Because of previously acquired contacts, each salesperson's efficiency in covering each region varies in terms of expected sales. The estimated sales per month (in thousands) by each salesperson for each region are:
Salesperson a b c d e
1 15 12 14 16 18
2 14 10 15 10 14
3 16 13 10 19 16
4 18 17 12 17 14
5 12 16 10 14 13
Find the optimal assignment using the Hungarian method.