C#:设置线程并获取函数返回值

我正在尝试创建一个控制台应用程序，该应用程序将为四个函数创建四个线程，然后获取函数将返回的内容。线程1必须计算一个充满随机数的数组的和并返回，线程2计算同一数组的乘积并返回，螺纹3创建并返回一个-10000之间的随机整数，第四个取sum、乘积和x（随机数），比较它们并显示谁比谁大。

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading;
    namespace threadsproject
    {
        class Program
        {
            public int thread1(int [] a, int n)
            {
                int i = n;
                int sum = 0;
            for (int j = 0; j < i; j++)
            {
                sum = a[j] + sum;
            }
            Console.WriteLine("'nThe sum is: ");
            return sum;
        }
            public int thread2(int[] a, int n)
            {
        int prod = 1;
        for (int j = 0; j < n; j++)
        {
            prod = a[j] * prod;
        }
        Console.WriteLine("'nThe product is: ");
        return prod;
    }
    public int thread3()
    {
        Random rnd = new Random();
        int x;
        x = rnd.Next(-1000, 1000);
        Console.WriteLine("'nYour random number is: {0}", x);
        return x;
    }
    public void thread4(int sum, int prod, int x)
    {
        Console.WriteLine("'n");
        if (sum < prod && prod < x)
        {
            Console.WriteLine("T1,T2,T3");
        }
        else if (sum < x && x < prod)
        {
            Console.WriteLine("T1,T3,T2");
        }
        else if (x < sum && sum < prod)
        {
            Console.WriteLine("T2,T1,T3");
        }
        else if (x < prod && prod < sum)
        {
            Console.WriteLine("T2,T3,T1");
        }
        else if (prod < sum && sum < x)
        {
            Console.WriteLine("T3,T1,T2");
        }
        else if(prod < sum && sum == x)
        {
            Console.WriteLine("T3,T1=T2");
        }
        if (sum < prod && prod == x)
        {
            Console.WriteLine("T1,T2==T3");
        }
        else
            Console.WriteLine("T3,T2,T1");
    }
    static void Main(string[] args)
    {
        Random rnd = new Random();
        string s;
        int n;
        int [] numbers = null;
        Console.WriteLine("Give the size of the array: ");
        s = Console.ReadLine();
        n = int.Parse(s);
        for(int i=0; i<n; i++)
        {
            numbers[i] = rnd.Next(-100, 100);
        }
        int sum, prod, x;
        Thread mythread1 = new Thread(delegate() { thread1(numbers, n); });
        Thread mythread2 = new Thread(delegate() { thread2(numbers, n); });
        Thread mythread3 = new Thread(() => thread3());
        Thread mythread4 = new Thread(delegate() { thread4(sum, prod, x); });
        mythread1.Start();
        mythread2.Start();
        mythread3.Start();
        mythread4.Start();
    }
}

}

因此，当我创建线程时，我会得到相同的错误：非静态字段、方法或属性"threadsproject.Program.thread<1,2,4>（int int int）'。我在visualstudio2013.net 4.6。由于没有很好的线程编程经验，我希望得到一些帮助来理解我做错了什么。提前感谢大家！