public async Task Book(IBook <string> activity)
        {
            activity.book("HOTEL");
            activity.BookingComplete();
            await Task.Delay(1000);

            activity.book("HOSPITAL");
            activity.BookingComplete();
            await Task.Delay(1000);

            activity.book("RESTAURANT");
            activity.BookingComplete();
            await Task.Delay(1000);

            activity.book("THEATRE");
            activity.BookingComplete();
            await Task.Delay(1000);


            //return Task.CompletedTask;
        }