What is typical of city tenement buildings

five to seven stories and occupied nearly all of the lot upon which it was built (usually 25 feet wide and 100 feet long, according to existing city regulations)

the answer is a) to be able to obey them.

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).