A survey on a sample of 25 new cars being sold at a local auto dealer was conducted to see which of the three popular options – air-conditioning, radio and power windows – were already installed. The survey found: 15 had air-conditioning, 2 had air-conditioning and power windows but not radios, 12 had radio, 6 had air-conditioning and radio but no power-windows, 11 had power-windows, 4 had radio and power windows, 3 had all three options What is the number of cars that had none of the options? (a) 1       (b) 2      (c) 3      (d) 4