Task: Question Generation
Input (English): Passage: By this time Hu Zongxian had almost collected his strength: Lu Tang had won a decisive victory in Taizhou south of Ningbo and came back to help deal with Xu Hai; while 6000 fresh aboriginal soldiers from Baojing and Yongshun were on its way to come to Hu Zongxian's aid. The imperial inspector Zhao Wenhua reiterated the emperor's wishes that surrender was not an option, so Hu Zongxian made a show of receiving Xu Hai's surrender while waiting for the opportune moment to strike. In the meantime Xu Hai had settled in the Shen Family Estate  of Pinghu, where he recruited up to 300 new followers by hosting banquets for his neighbours, adding to the thousand or more raiders still under his command and remnants of Chen Dong's group next to the estate. He grew increasingly recalcitrant, refusing an invitation to an official Mid-Autumn party and even killing an envoy from Hu Zongxian. In late September, reinforcements from Baojing and Yongshun arrived and began small-scale skirmishes around the Shen Family Estate. Before commencing the final attack, Hu Zongxian persuaded his captive Chen Dong to write a letter to his followers encamped next to Xu Hai's forces, warning them that Xu Hai was conspiring with government troops to wipe them out in a pincer operation. This provoked Chen Dong's men into attacking Xu Hai's group on September 27, upon which government forces entered the fray from all directions, killing indiscriminately. On September 29, the battle ended with up to 1600 marauders killed in the estate, and Xu Hai's body was found in a nearby stream. On October 10, Chen Dong, Ye Ma, and Xu Hai's hostage brother were all executed in Jiaxing, marking the end of the wokou invasion of 1556.
Output (English): How many days did the battle between Chen Dong and Xu Hai last?