public class Order 

{

  // ...

  public double Price(int i) 

  {

    double primaryBasePrice;

    double secondaryBasePrice;

    double tertiaryBasePrice;

    // Perform long computation.

        // if i == 0, then do add

        // if i == 1, then do minus

        // if i == 2, then do Multiple

        // if i == 3, then do Devide

    // if i > 3, then do nothing "I can't do this calculation"

  }

}