为什么我不能在arraylist中使用getFixed方法？我怎样才能使它工作？

 import java.util.*;
 public class MainFile{
 public static void main(String[] args){
    ArrayList<TypeExpences> listOfTypes = new ArrayList<TypeExpences>();
    Water waterExp = new Water(0, "fafasd", 10, "cubic meters", 2, 1);
    listOfTypes.add(waterExp);
    System.out.println((listOfTypes.get(0)).getFixed());
    }
}

public class Water extends UseExpences{
    int pricePer2;  
    public Water(int kod, String descr, int fixed, String unit, int 
     pricePer, int pricePer2){
    super(kod, descr, fixed, unit, pricePer);
    this.pricePer2 = pricePer2;
    }
   public int getFixed(){
   return super.getFixedPrice(fixedPrice);
   }
}

public class UseExpences extends TypeExpences{
    protected int fixedPrice;
    protected String unitOfMeasurement;
    protected int pricePerMeasurementUnit;

    public UseExpences(int kod, String descr, int fixed, String unit, int 
     pricePer){
        super(kod, descr);
        fixedPrice = fixed;
        unitOfMeasurement = unit;
        pricePerMeasurementUnit = pricePer;
    }

    public int getFixedPrice(int fixedPrice){
        return fixedPrice;
    }
}

public class TypeExpences {
    protected int code;
    protected String description;
    public TypeExpences(int kod, String descr){
        code = kod;
        description = descr;
    }
    protected int getCode(int code){
        return code;
    }
    protected String getDescription(String description){
        return description;
    }
}
 import java.util.*;
 public class MainFile{
 p