[Retros] Add units, 18th update

[Mu-Tsun Tsai]

Hi Alain,

I'm kind of hesitate to say this... but I believe the new 1KA problem is 
really my own creation and multi-ownership is not needed. Similarly the 1NA 
is basically just Andrew Buchanann (or, after me at most). Of course you 
should ask Andrew's opinion on this one.

Mu-Tsun