|Date|Number|Type|Captain|Casualties|Sunk by|
|---|---|---|---|---|---|
|4 May 1943|U-209|VIIC|Heinrich Brodda|46|Catalina Flying-boat of No. 5 Squadron RCAF|
|5 May 1943|U-638|VIIC|Oskar Staudinger|44|HMS Sunflower|
|5 May 1943|U-531|IXC/40|Herbert Neckel|54|HMS Vidette|
|6 May 1943|U-192|IXC/40|Werner Happe|55|HMS Loosestrife|
|6 May 1943|U-125|IXC|Ulrich Folkers|54|HMS Oribi, HMS Snowflake|
|6 May 1943|U-630|VIIC|Werner Winkler|47|HMS Vidette|
|6 May 1943|U-438|VIIC|Heinrich Hensohn|48|HMS Pelican|

Question: how many captains are listed?
Answer: 7