A major bank warned on Wednesday that weeks of protests in Hong Kong could hit the economies of the Chinese-ruled city and mainland China itself as demonstrators prepared a sit-in at a subway and site of a mid-summer mob attack. Hong Kong-based Bank of East Asia Ltd (BEA) posted a 75% slump in first-half net profit after it wrote down loans in China because of a downturn in commercial property markets outside China’s top cities. It also warned that social unrest in Hong Kong and a trade dispute between China and the United States could affect the economies of China and the former British colony.