public static void Main()
Console.WriteLine("The answer is : " + calc.Sum(a, b).ToString());
Console.WriteLine("The answer is : " + calc.Mult(a, b).ToString());
Console.WriteLine("The answer is : " + calc.Dev(a, b).ToString());
internal int Sum(int a, int b)
internal int Mult(int a, int b)
internal int Dev(int a, int b)