Getting the sum of 2 different indices from 2 seperate Array’s, JAVA

Very new to Java, so please bear with me here. I have to write a program based on the resident status of a student to determine the total cost for the term. I must use Abstract methods (separate class), and then create a classes based on Tuition for Full time and Part Time. The full and part time classes must use Array’s. I probably wrote the Array list wrong, but this is what I have so far, and I need to create an object “county” so I can calculate the cost for the student who resides in the county. How do I call the tuition and capital fee to add them together for the index C only? Or, would it be easier if I write an array for just county with the tuition and capital fee then sum those together, then add that total to the other costs listed? Also, when I try to create the object under county, it comes up with an error. I will be using Radio Buttons to determine what the resident status of the student is, (not sure if that changes things for my calculations). Any help is appreciated.

The abstract class:

package collegecost1;

public abstract class collegeAbMain 
public abstract double tuition();
public abstract double capitalFee();
public abstract double accidentIns();
public abstract double collegeFee();

//public abstract double county();
//public abstract double outCounty();
//public abstract double outState();


fullTime class

 package collegecost1;

 public class fullTime extends collegeAbMain 
double  C;
double OC;
double OS;
double Ins;
double fee;
double total;

public double tuition() 
    double resident = 3;
    double [] tuition = new double [(int) resident];

    // I have to use the variables C, OC, and OS
    tuition[0] = C;
    C = 1571.25;

    tuition[1] = OC;
    OC = 3142.50;

    tuition[2] = OS;
    OS = 4713.75;
    return resident;

public double capitalFee() 
    double resident = 3;
    double[] capitalFee = new double [(int) resident];

    capitalFee[0] = C;
    C = 0.00;

    capitalFee[1] = OC;
    OC = 78.00;

    capitalFee[2] = OS;
    OS = 78.00;

    return resident ;
public double accidentIns() 
    Ins = 0.00;
    return Ins;
public double collegeFee() 
    fee = 50.40;
    return fee;

public double county()
     county total = new county()
//ERROR (wants me to create class or interface for the 1st word county
    // have written objects the exact same way in other programs and never
    // had an issue. 

              //total = (index[0] from resident tution +
      //index [0] from resident caplitalFee)
              //+ (Ins) + (fee);

          return total();