<Tr> <Td> 2005 </Td> <Td> 901,463 </Td> <Td> 69,549 </Td> </Tr> <Tr> <Td> 2006 </Td> <Td> 796,039 </Td> <Td> 72,128 </Td> </Tr> <Tr> <Td> 2007 </Td> <Td> 690,589 </Td> <Td> 73,618 </Td> </Tr> <Tr> <Td> 2008 </Td> <Td> 515,513 </Td> <Td> 67,749 </Td> </Tr>

What does the f in f150 stand for