Task: Question Generation
Input (English): Passage: Ava's authority deteriorated further in Shwenankyawshin's reign . Three of the king's own brothers openly raised a rebellion in 1501. Mohnyin, Ava's former vassal, now began to raid its territory. In 1507, Ava ceded to Mohnyin all northern Avan territory down to present-day Shwebo in the vain hope that the raids would stop. It did not. Ava desperately tried to retain Toungoo's loyalty by ceding the key Kyaukse granary to Toungoo but it too failed. Toungoo took the region but formally broke away in 1510. Ava's only ally was the Shan state of Thibaw , which too was fighting Mohnyin's raids on its territory. Mohnyin was attacking other Shan states when it was not raiding Ava. It seized Bhamo from Thibaw in 1512 in the east, and raiding Kale in the west. The Ava-Thibaw alliance was able to retake Shwebo for a time but Mohnyin proved too strong. By the early 1520s, Chief Sawlon of Mohnyin had assembled a confederation of Shan states  under his leadership. Prome had also joined the confederation. The confederation wiped out Ava's defences in Shwebo in 1524. Finally on 25 March 1527, the forces of the confederation and Prome took Ava. The Confederation later sacked Prome in 1533 because Sawlon felt that Prome had not given sufficient help.
Output (English): How many years after the forces of the confederation and Prome took Ava did the Confederation sack Prome because Sawlon felt that Prome had not given sufficient help?