Edge of tomrrow - how many Alphas are there?

In the movie Tom kills an Alpha and gets the Alphas powers. Then the movie magic happens.

My queston is 2 part.

1. 
   

   Is it ever mentioned in the movie how many Alphas there are ( Emily killed one too )?

   
   


2. 
   

   Do they ever discuss the possability of actively searching for other Alphas to reprodce the effect?