public static HOADON LapHoaDon(PHIEUGHIDIEN P, DINHMUC[] QuiTac)
    {
        HOADON kq;

        kq.HoTen = P.HoTen;
        kq.SoKw  = P.SoKw;
        long a = 0;
        long d = 0;

        for (; d < QuiTac.Length; d++)
        {
            if (a <= P.SoKw && P.SoKw <= QuiTac[d].GiaTri)
            {
                break;
            }
            a = a + QuiTac[d].GiaTri;
        }
        d++;
        kq.SuDung = new DINHMUC[d];

        for (; d != 0; d--)
        {
            kq.SuDung[d - 1] = QuiTac[d - 1];
        }
        kq.TongTien = XuLyQuiTac.TinhTien(QuiTac, P.SoKw);
        return(kq);
    }
    public static String XuatChuoi(HOADON P)
    {
        String Chuoi = "Ho ten nguoi su dung: " + P.HoTen + "\n";

        Chuoi = Chuoi + "Da su dung :" + P.SoKw;
        Chuoi = Chuoi + " Kw nam trong cac don gia sau:\n" + XuLyQuiTac.XuatChuoi(P.SuDung);
        Chuoi = Chuoi + "\nTong so tien phai tra: " + XuLySoThuc.XuatChuoi(P.TongTien) + " dong";
        return(Chuoi);
    }
    static void Main(string[] args)
    {
        DINHMUC[] P     = XuLyQuiTac.Doc("HoaDonTienDien.txt");
        String    Chuoi = "Du lieu khong hop le";

        if (P != null)
        {
            PHIEUGHIDIEN Phieu;
            Phieu = XuLyPhieuGhiDien.Nhap("Nhap thong tin cua phieu ghi dien:\n");
            HOADON kq;
            kq    = XuLyHoaDon.LapHoaDon(Phieu, P);
            Chuoi = "\nKhach hang co thong tin:\n" + XuLyPhieuGhiDien.XuatChuoi(Phieu);
            Chuoi = Chuoi + "\n\nCo hoa don tien dien la:\n" + XuLyHoaDon.XuatChuoi(kq);
        }
        XuLyChuoi.Xuat(Chuoi);
    }