On 24 March 2009, the Nigerian Federal Ministry of Science and Technology, NigComSat Ltd. and CGWIC signed another contract for the in-orbit delivery of the NigComSat-1R satellite. NigComSat-1R was also a DFH-4 satellite, and the replacement for the failed NigComSat-1 was successfully launched into orbit by China in Xichang on December 19, 2011. The satellite according to then-Nigerian President Goodluck Jonathan which was paid for by the insurance policy on NigComSat-1 which de-orbited in 2009, would have a positive impact on national development in various sectors such as communications, internet services, health, agriculture, environmental protection and national security.

Answer this question, if possible (if impossible, reply "unanswerable"): Where was Nigeria's fourth satellite launched?
China