text: #include <string>
  #include <vector>
  using namespace std;
  class Activity
  {
  private:
  
  public:
  	Activity(void);
  	~Activity(void);
  
  //data
  	static int activity_coefficient(int f, double T, double P, vector<string> ListName, vector<double> ListMole, vector<double> &ListLGAMMA, double &AW);
  	//f - flag for activity coefficients methods
  	//1 - D-H limiting law
  	//2 - Revised D-H equation
  	//3 - Guggenheim equation
  	//4 - Davies equation
  	//5 - Extend D-H equation
  	//6 - Truesdell-Jones equation (T-J)
  	//7 - Specific ion interaction theory (SIT)
  	//8 - Bromley equation
  	//9 - Helgeson equation
  	//10- Pitzer equation
  	//11- B-dot
  	static double  Ar(double T, double P);
  	static double  Br(double T, double P);
  	static void entrance(void);
  };
  