Solution
This is the cost matrix.
| 51 | 52 | 71 | 59 | 44 | 12 | 61 | 91 | 80 |
| 85 | 83 | 87 | 26 | 44 | 48 | 35 | 69 | 20 |
| 27 | 46 | 48 | 96 | 95 | 78 | 30 | 52 | 98 |
| 45 | 22 | 88 | 22 | 6 | 48 | 83 | 19 | 49 |
| 47 | 23 | 70 | 97 | 18 | 57 | 73 | 22 | 77 |
| 22 | 66 | 44 | 57 | 37 | 28 | 78 | 91 | 72 |
| 53 | 2 | 93 | 18 | 13 | 71 | 11 | 37 | 57 |
| 54 | 84 | 6 | 42 | 8 | 28 | 27 | 27 | 94 |
| 77 | 51 | 99 | 8 | 11 | 28 | 58 | 99 | 18 |
Subtract row minima
For each row, the minimum element is subtracted from all elements in that row.
| 39 | 40 | 59 | 47 | 32 | 0 | 49 | 79 | 68 | (-12) |
| 65 | 63 | 67 | 6 | 24 | 28 | 15 | 49 | 0 | (-20) |
| 0 | 19 | 21 | 69 | 68 | 51 | 3 | 25 | 71 | (-27) |
| 39 | 16 | 82 | 16 | 0 | 42 | 77 | 13 | 43 | (-6) |
| 29 | 5 | 52 | 79 | 0 | 39 | 55 | 4 | 59 | (-18) |
| 0 | 44 | 22 | 35 | 15 | 6 | 56 | 69 | 50 | (-22) |
| 51 | 0 | 91 | 16 | 11 | 69 | 9 | 35 | 55 | (-2) |
| 48 | 78 | 0 | 36 | 2 | 22 | 21 | 21 | 88 | (-6) |
| 69 | 43 | 91 | 0 | 3 | 20 | 50 | 91 | 10 | (-8) |
Subtract column minima
For each column, the minimum element is subtracted from all elements in that column.
| 39 | 40 | 59 | 47 | 32 | 0 | 46 | 75 | 68 |
| 65 | 63 | 67 | 6 | 24 | 28 | 12 | 45 | 0 |
| 0 | 19 | 21 | 69 | 68 | 51 | 0 | 21 | 71 |
| 39 | 16 | 82 | 16 | 0 | 42 | 74 | 9 | 43 |
| 29 | 5 | 52 | 79 | 0 | 39 | 52 | 0 | 59 |
| 0 | 44 | 22 | 35 | 15 | 6 | 53 | 65 | 50 |
| 51 | 0 | 91 | 16 | 11 | 69 | 6 | 31 | 55 |
| 48 | 78 | 0 | 36 | 2 | 22 | 18 | 17 | 88 |
| 69 | 43 | 91 | 0 | 3 | 20 | 47 | 87 | 10 |
| | | | | | (-3) | (-4) | |
Cover all zeros with a minimum number of lines
A total of 9 lines are required to cover all zeros.
| 39 | 40 | 59 | 47 | 32 | 0 | 46 | 75 | 68 | x |
| 65 | 63 | 67 | 6 | 24 | 28 | 12 | 45 | 0 | x |
| 0 | 19 | 21 | 69 | 68 | 51 | 0 | 21 | 71 | x |
| 39 | 16 | 82 | 16 | 0 | 42 | 74 | 9 | 43 | x |
| 29 | 5 | 52 | 79 | 0 | 39 | 52 | 0 | 59 | x |
| 0 | 44 | 22 | 35 | 15 | 6 | 53 | 65 | 50 | x |
| 51 | 0 | 91 | 16 | 11 | 69 | 6 | 31 | 55 | x |
| 48 | 78 | 0 | 36 | 2 | 22 | 18 | 17 | 88 | x |
| 69 | 43 | 91 | 0 | 3 | 20 | 47 | 87 | 10 | x |
The optimal assignment
Because there are 9 lines required, an optimal assignment exists among the zeros.
| 39 | 40 | 59 | 47 | 32 | 0 | 46 | 75 | 68 |
| 65 | 63 | 67 | 6 | 24 | 28 | 12 | 45 | 0 |
| 0 | 19 | 21 | 69 | 68 | 51 | 0 | 21 | 71 |
| 39 | 16 | 82 | 16 | 0 | 42 | 74 | 9 | 43 |
| 29 | 5 | 52 | 79 | 0 | 39 | 52 | 0 | 59 |
| 0 | 44 | 22 | 35 | 15 | 6 | 53 | 65 | 50 |
| 51 | 0 | 91 | 16 | 11 | 69 | 6 | 31 | 55 |
| 48 | 78 | 0 | 36 | 2 | 22 | 18 | 17 | 88 |
| 69 | 43 | 91 | 0 | 3 | 20 | 47 | 87 | 10 |
This corresponds to the following optimal assignment in the original cost matrix.
| 51 | 52 | 71 | 59 | 44 | 12 | 61 | 91 | 80 |
| 85 | 83 | 87 | 26 | 44 | 48 | 35 | 69 | 20 |
| 27 | 46 | 48 | 96 | 95 | 78 | 30 | 52 | 98 |
| 45 | 22 | 88 | 22 | 6 | 48 | 83 | 19 | 49 |
| 47 | 23 | 70 | 97 | 18 | 57 | 73 | 22 | 77 |
| 22 | 66 | 44 | 57 | 37 | 28 | 78 | 91 | 72 |
| 53 | 2 | 93 | 18 | 13 | 71 | 11 | 37 | 57 |
| 54 | 84 | 6 | 42 | 8 | 28 | 27 | 27 | 94 |
| 77 | 51 | 99 | 8 | 11 | 28 | 58 | 99 | 18 |
The total minimum cost is 128.