What was the average number of old houses in rural areas before Xuzhou?

Generally, a room is 20-30 square meters.

Xuzhou is located in the southeast of North China Plain and the northwest of Jiangsu Province. The Beijing-Hangzhou Grand Canal passes through it, and the Longhai Railway and beijing-shanghai railway meet here. It is known as the thoroughfare of five provinces. Xuzhou is an important gateway city in East China, an important economic, scientific, educational, cultural, financial, medical and foreign trade center in East China, an important node city of the National Belt and Road, a sub-central city in the northern wing of the Yangtze River Delta, a core city in Xuzhou metropolitan area and an international new energy base. It has the reputation of "China Construction Machinery Capital".