<Tr> <Td> May 15, 1987 </Td> <Td> 2,320 </Td> <Td> + 20 </Td> </Tr> <Tr> <Td> August 10, 1987 </Td> <Td> 2,352 </Td> <Td> + 32 </Td> </Tr> <Tr> <Td> September 29, 1987 </Td> <Td> 2,800 </Td> <Td> + 448 </Td> <Td> Pub. L. 100--119 </Td> </Tr> <Tr> <Td> August 7, 1989 </Td> <Td> 2,870 </Td> <Td> + 70 </Td> </Tr>

Which of the following is the biggest holder of us federal government debt