A Perfect Program to Calculate Average and Percentage

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication1
{
    class CalcAvgPerc //Calculate the Average marks and percentage for students
    {
        public float maths, science, english, physics, chemistry;
        public float average, percentage, total = 500f;
        static void Main(string[] args)
        {
            String StudentName;
            Console.WriteLine("Enter the name for Student to Calculate the Average and Percentage");
            StudentName = Console.ReadLine();
            Console.WriteLine("Creating Report for the student :{0}", StudentName);
            System.Threading.Thread.Sleep(5000);
            Console.WriteLine("Validating Marks....");
            CalcAvgPerc a = new CalcAvgPerc();
            a.abc();
        }
        public void abc()
        {
            Console.WriteLine("Enter Marks for Maths for range 0-100");
            maths = float.Parse(Console.ReadLine());
            Console.WriteLine("Enter Marks for Science for range 0-100");
            science = float.Parse(Console.ReadLine());
            Console.WriteLine("Enter Marks for English for range 0-100");
            english = float.Parse(Console.ReadLine());
            Console.WriteLine("Enter Marks for Physics for range 0-100");
            physics = float.Parse(Console.ReadLine());
            Console.WriteLine("Enter Marks for Chemistry for range 0-100");
            chemistry = float.Parse(Console.ReadLine());
            if ((maths >= 0 && maths <= 100) && (science >= 0 && science <= 100) && (english >= 0 && english <= 100) && (physics >= 0 && physics <= 100) && (chemistry >= 0 && chemistry <= 100))
            {
                System.Threading.Thread.Sleep(3000);
                average = (maths + science + english + physics + chemistry) / total;
                Console.WriteLine("Average score is :{0}", average);
                percentage = average * 100;
                Console.WriteLine("Percentage obtained by student is: {0}", percentage);
                Console.ReadLine();
            }
            else
            {
                Console.WriteLine("Marks Entered are incorrect...Re-enter the Marks");
                abc();
            }
        }
    }
}