По какому правилу сформирован массив b?

• For i:= 1 to N do
  b
  \[i\]
  :=a
  \[i\]
  *2;
• For i:= 8 downto 1 do
  b
  \[i\]
  :=a
  \[i\]
  *2;
• for i:=1 to N div 2 do begin
  x := a
  \[i\]
  ;
  b
  \[i\]
  := a
  \[N\-i\+1\]
  ;
  b
  \[N\-i\+1\]
  := x*2;
  end;
• for i:=1 to N div 2 do begin
  x := a
  \[i\]
  ;
  b
  \[i\]
  := a
  \[N\-i\+1\]
  *2;
  b
  \[N\-i\+1\]
  := x*2;
  end;