context: Volga-Kama cascade of hydroelectric power stations is a cascade of reservoirs and hydroelectric power stations in the Volga river basin. All objects of the cascade are located on the territory of Russia. Organizationally includes 13 hydropower plants on the Volga, Kama and Sheksna, of which 12 include hydroelectric power plants [1].
question: How many hydropower plants are included in the Volga-Kama cascade?
answers.text: 12