Tesla Inc. says buyers must order cars by Monday to get the full federal electric vehicle tax credit of $7,500. The company says on its website that cars ordered by Monday will be delivered by the end of the year. Under federal law, buyers get the full credit until a manufacturer reaches 200,000 vehicles sold since the start of 2010. Tesla hit 200,000 in July but the full credit continues for vehicles delivered by Dec. 31. Then it is gradually phased out.