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:
| Location | Name of mill and\ngrid reference | Type | Maps | First mention\nor built | Last mention\nor demise |
| --- | --- | --- | --- | --- | --- |
| Chesfield |  | Post |  | 1318 | 1372 |
| Chesfield | Chesfield Park | Titt iron wind engine |  | 1896 |  |
| Cheshunt | TL 317 036 | Post |  | 1843 | Demolished c. 1860 |
| Cheshunt | Goff's Oak Mill\nTL 317 036 | Tower |  | c. 1860 | Demolished 1953 |
| Cheshunt | Turner's Hill Mill\nTL 363 023 |  | 1822 | 1822 | 1861 |
| Chipperfield | TL 037 014 | Post |  | 1594 | 1594 |
| Chipperfield | TL 037 014 | Smock | 1822 | 1822 | 1881, gone by 1896 |
| Chipping | Approximately\nTL 350 319 | Post | 1720\n1728 | 1720 | 1728 |
| Clothall | Approximately\nTL 264 326 | Post |  | 1370 | 1370 |
| Codicote | Codicote Heath\nApproximately\nTL 206 185 | Smock |  | 1841 | 1855, gone by 1881 |
| Colney Heath | Colney Heath Mill\nTL 205 055 | Tower |  | 1854 | Windmill World |
| Cottered |  | Post |  | 1581 | 1581 |
| Cromer |  |  |  | 1192 | 1576 |
| Cromer | Cromer Mill\nTL 304 286 | Post | 1720\n1728\n1749\n1766\n1800\n1822 | 1720 | Windmill World |
| Croxley Green | Croxley Green Mill\nTQ 067 953 | Tower |  | c. 1860 | Windmill World |
Question:
how man "c" windmills have there been?
Answer:
15