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:
| Date | Name of ship | Nationality | Tonnage | Fate |
| --- | --- | --- | --- | --- |
| 5 June 1940 | SS Stancor | United Kingdom | 798 | Sunk at 58°48′N 08°45′W﻿ / ﻿58.800°N 8.750°W |
| 7 June 1940 | SS Frances Massey | United Kingdom | 4,212 | Sunk at 55°33′N 08°26′W﻿ / ﻿55.550°N 8.433°W |
| 7 June 1940 | SS Eros | United Kingdom | 5,888 | Damaged at 55°33′N 08°26′W﻿ / ﻿55.550°N 8.433°W |
| 11 June 1940 | SS Violando N Goulandris | Greece | 2,375 | Sunk at 44°04′N 12°30′W﻿ / ﻿44.067°N 12.500°W |
| 19 June 1940 | MV Tudor | Norway | 6,607 | Sunk at 45°10′N 11°50′W﻿ / ﻿45.167°N 11.833°W |
| 19 June 1940 | SS Baron Loudoun | United Kingdom | 3,164 | Sunk at 45°00′N 11°21′W﻿ / ﻿45.000°N 11.350°W |
| 19 June 1940 | SS British Monarch | United Kingdom | 5,661 | Sunk at 45°00′N 11°21′W﻿ / ﻿45.000°N 11.350°W |
| 20 June 1940 | MV Moerdrecht | Netherlands | 7,493 | Sunk at 43°34′N 14°20′W﻿ / ﻿43.567°N 14.333°W |
| 16 August 1940 | SS Hedrun | Sweden | 2,325 | Sunk at 57°10′N 16°37′W﻿ / ﻿57.167°N 16.617°W |
| 19 August 1940 | SS Ville de Gand | Belgium | 7,590 | Sunk at 55°28′N 15°10′W﻿ / ﻿55.467°N 15.167°W |
| 24 August 1940 | SS La Brea | United Kingdom | 6,666 | Sunk at 57°24′N 11°21′W﻿ / ﻿57.400°N 11.350°W |
| 25 August 1940 | SS Empire Merlin | United Kingdom | 5,763 | Sunk at 58°30′N 10°15′W﻿ / ﻿58.500°N 10.250°W |
| 25 August 1940 | MV Athelcrest | United Kingdom | 6,825 | Sunk at 58°24′N 11°25′W﻿ / ﻿58.400°N 11.417°W |
Question:
number of boats that were attacked by hans-rudolf rosing as a u-boat commander
Answer:
13