text: You are playing Starcraft-II. Your task is to control our two marines, namely marine 1 and marine 2, to wipe out two marines of the enemy, namely marine 3 and marine 4. 
  
  Our two marines, marine 1 and marine 2, can take the following action:
  A. attack marine 3
  B. attack marine 4
  
  To  make marine 1 and 2 concentrate fire, which action should marine 1 take? which action should marine 2 take?