public int ReturnCar(string vehicleRego)
        {
            int cuscar = 0;
            List<string> mylist = new List<string> { };
            List<string> separatelist1 = new List<string> { };
            string s = "";
            if(rentals.ContainsKey(vehicleRego))
            {
                foreach (KeyValuePair<string, int> car in rentals)
                {
                    s = car.Key + "," + car.Value.ToString();
                    mylist.Add(s);
                }
                for (int i = 0; i < mylist.Count(); i++)
                {
                    if (mylist[i].Split(',').ToList().Contains(vehicleRego))
                    {
                        cuscar = int.Parse(mylist[i].Split(',').ToList()[1]);
                        mylist.Remove(mylist[i]);
                        i--;
                    };
                };
                rentals.Clear();
                for (int a = 0; a < mylist.Count(); a++)
                {
                    separatelist1 = mylist[a].Split(',').ToList();
                    if (int.TryParse(separatelist1[1], out myvalue) == true)
                    {
                        mykey = separatelist1[0];
                        myvalue = int.Parse(separatelist1[1]);
                        rentals.Add(mykey, myvalue);
                        separatelist1.Clear();
                    }
                }
            }
            if (!rentals.ContainsKey(vehicleRego) && cuscar == 0)
            {
                cuscar = -1;
            };
            return cuscar;
        }