Java循环问题声明变量

Question

我遇到以下代码的问题。

我需要使附加费变量等于给定特定结果的两个值之一，而我似乎只能将我的附加值等于R_RATE。

我哪里错了？

   String booking;
   double AddOn, trip, surcharge;  

   System.out.print("Enter booking type (A, B or C)");
   booking=sc.nextLine();

   double R_RATE_PERCENT = .5;
   double R_RATE = 5.0;

   if (booking.equals("A")
   {surcharge = S_Rate;

   if(booking.equals("B"))
   {       
   addOn = R_RATE;   

      if (addOn > trip * R_RATE_PERCENT) { 
      surcharge = trip * R_RATE_PERCENT;}

      else if (addOn < trip * R_RATE_PERCENT){
               surcharge = R_RATE;}
    }

   if(booking.equals("C"))
   {       
   addOn = F_RATE;   

      if (addOn > trip * F_RATE_PERCENT) { 
      surcharge = trip * F_RATE_PERCENT;}

      else if (addOn < trip * F_RATE_PERCENT){
               surcharge = F_RATE;}