Solution
This is the cost matrix.
| 83 | 1 | 14 | 11 |
| 12 | 14 | 10 | 34 |
| 76 | 93 | 45 | 32 |
| 65 | 86 | 16 | 92 |
Subtract row minima
For each row, the minimum element is subtracted from all elements in that row.
| 82 | 0 | 13 | 10 | (-1) |
| 2 | 4 | 0 | 24 | (-10) |
| 44 | 61 | 13 | 0 | (-32) |
| 49 | 70 | 0 | 76 | (-16) |
Subtract column minima
For each column, the minimum element is subtracted from all elements in that column.
| 80 | 0 | 13 | 10 |
| 0 | 4 | 0 | 24 |
| 42 | 61 | 13 | 0 |
| 47 | 70 | 0 | 76 |
| (-2) | | | |
Cover all zeros with a minimum number of lines
A total of 4 lines are required to cover all zeros.
| 80 | 0 | 13 | 10 | x |
| 0 | 4 | 0 | 24 | x |
| 42 | 61 | 13 | 0 | x |
| 47 | 70 | 0 | 76 | x |
The optimal assignment
Because there are 4 lines required, an optimal assignment exists among the zeros.
| 80 | 0 | 13 | 10 |
| 0 | 4 | 0 | 24 |
| 42 | 61 | 13 | 0 |
| 47 | 70 | 0 | 76 |
This corresponds to the following optimal assignment in the original cost matrix.
| 83 | 1 | 14 | 11 |
| 12 | 14 | 10 | 34 |
| 76 | 93 | 45 | 32 |
| 65 | 86 | 16 | 92 |
The total minimum cost is 61.