Query: In what year did Ma Yuan die?
Context: The Trưng Sisters of Vietnam rebelled against Han in AD 40. Their rebellion was crushed by Han general Ma Yuan (d. AD 49) in a campaign from AD 42–43. Wang Mang renewed hostilities against the Xiongnu, who were estranged from Han until their leader Bi (比), a rival claimant to the throne against his cousin Punu (蒲奴), submitted to Han as a tributary vassal in AD 50.