Why Russians Are Dumping Chinese Yuan to Save the Ruble - Econ Lessons

The ruble and the Chinese yuan are falling. Russia is selling Chinese currency to support the ruble against the dollar. Why is Moscow doing this? The Russian Ruble is in stage 4 decline, as evidenced by the 200-moving average and the asset price. To prop it up, the Russian central bank is actively selling Chinese currency reserves. How long can this continue, and how much does it cost? What does this tell about each economy based on monetary economic theory?