Code?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace PlanetLibrary
{
    public class Planet : PlanetMaths
    {

        //Variables
        double Radius = 0;
        double Surface = 0;
        double Atmosphere = 0;
        double Speed = 0;
        double DistanceQ = 0;
        double Mass = 0;
        double Weight = 0;
        int YearInDays = 0;
        int Time = 0;
        double Circle = 0;
        string stringHolder = "";
        double ans = 0;

        public Planet()
        {
        }

        public void setRadius(double PlanetRadius)
        {
            Radius = PlanetRadius;
        }

        public double getRadius()
        {
            return Radius;
        }

        public void setSurface(double PlanetSurface)
        {
            Surface = PlanetSurface;
        }

        public double getSurface()
        {
            return Surface;
        }

        public void setAtmosphere(double PlanetAtmosphere)
        {
            Atmosphere = PlanetAtmosphere;
        }

        public double getAtmospehere()
        {
            return Atmosphere;
        }

        public void setSpeed(double PlanetSpeed)
        {
            Speed = PlanetSpeed;
        }

        public double getSpeed()
        {
            return Speed;
        }

        public void setDistance(double PlanetDistance)
        {
            DistanceQ = PlanetDistance;
        }

        public double getDistance()
        {
            return DistanceQ;
        }

        public void setMass(double Mass)
        {
            Weight = Mass;
        }

        public double getMass()
        {
            return Mass;
        }

        public void setYearInDays(int YearInDays)
        {
            Time = YearInDays;
        }

        public double getYearInDays()
        {
            return YearInDays;
        }

    }

    public class PlanetMaths : GeneralMaths
    {

        public PlanetMaths()
        {

        }

        public static string PlanetMass(string surfaceType, double radius)
        {
            string stringHolder;
            double answer;
            if(surfaceType == "Rock")
            {
                answer =  * 2002.00;
            }

            else if (surfaceType == "Gas")
            {

            }
            else
            {

            }

        }
    }

    public class GeneralMaths
    {

        public GeneralMaths()
        {

        }

        public double Volume (double radius)
        {
            double answer;
            answer = (4 / 3) * (Math.PI) * (radius * radius * radius);
            return answer;
        }

        public double Distance(double radius)
        {
            double answer;
            answer = 2 * (Math.PI) * radius;
            return answer;
        }
    }

 //  class Display
 //  {
 //
 //      Console.WriteLine("|-------------------------------|");
 //      Console.WriteLine("|      Planet Calculator        |");
 //      Console.WriteLine("|-------------------------------|");
 //      Console.WriteLine("");
 //      Console.WriteLine("|-------------------------------|");
 //  }

}