<Tr> <Td> </Td> <Td> Spiro Agnew </Td> <Td> January 20, 1969--October 10, 1973 </Td> <Td> President of the Senate </Td> </Tr> <Tr> <Td> </Td> <Td> James Eastland </Td> <Td> October 10--December 6, 1973 </Td> <Td> President pro tempore </Td> </Tr> <Tr> <Td> </Td> <Td> Gerald Ford </Td> <Td> December 6, 1973--August 9, 1974 </Td> <Td> President of the Senate </Td> </Tr> <Tr> <Td> </Td> <Td> James Eastland </Td> <Td> August 9--December 19, 1974 </Td> <Td> President pro tempore </Td> </Tr>

Who is the presiding officer in the u.s. senate