static void Main(string[] args)
{
box a = new box(); //first box
a.h = 4; //height
a.l = 2; //length
a.w = 9; //width
box b = new box(); //second box
b.w = 5;
b.l = 3;
b.h = 6;
box z = new box(); // another object to receive value from operator
z = a + b;
Console.WriteLine("NEW VOLUME = " + z.volume());
}