Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Rank | City | Population | Area\n(km2) | Density\n(inhabitants/km2) | Altitude\n(mslm) |
| --- | --- | --- | --- | --- | --- |
| 1st | Alessandria | 94191 | 203.97 | 461.8 | 95 |
| 2nd | Casale Monferrato | 36039 | 86.32 | 417.5 | 116 |
| 3rd | Novi Ligure | 28581 | 54.22 | 527.1 | 197 |
| 4th | Tortona | 27476 | 99.29 | 276.7 | 122 |
| 5th | Acqui Terme | 20426 | 33.42 | 611.2 | 156 |
| 6th | Valenza | 20282 | 50.05 | 405.2 | 125 |
| 7th | Ovada | 11912 | 35.33 | 337.2 | 186 |
| 8th | Serravalle Scrivia | 6445 | 16.02 | 402.3 | 225 |
| 9th | Arquata Scrivia | 6260 | 30.36 | 206.2 | 248 |
| 10th | Castelnuovo Scrivia | 5473 | 45.42 | 120.5 | 85 |
Question:
how many cities have densities at least above 400?
Answer:
6