In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
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Question: Which trade route connected Northern Europe and Northwestern Russia with the Capsian Sea?, Context: The new Kievan state prospered due to its abundant supply of furs, beeswax, honey, and slaves for export, and because it controlled three main trade routes of Eastern Europe. In the north, Novgorod served as a commercial link between the Baltic Sea and the Volga trade route to the lands of the Volga Bulgars, the Khazars, and across the Caspian Sea as far as Baghdad, providing access to markets and products from Central Asia and the Middle East. Trade from the Baltic also moved south on a network of rivers and short portages along the Dnieper known as the "route from the Varangians to the Greeks," continuing to the Black Sea and on to Constantinople. Kiev was a central outpost along the Dnieper route and a hub with the east-west overland trade route between the Khazars and the Germanic lands of Central Europe. These commercial connections enriched Rus' merchants and princes, funding military forces and the construction of churches, palaces, fortifications, and further towns. Demand for luxury goods fostered production of expensive jewelry and religious wares, allowing their export, and an advanced credit and money-lending system may have also been in place.

Answer: Volga trade route


Question: What is a legal doctrine that obligates courts to follow historical cases when making a ruling on a similar case, Context: Federal law originates with the Constitution, which gives Congress the power to enact statutes for certain limited purposes like regulating interstate commerce. The United States Code is the official compilation and codification of the general and permanent federal statutes. Many statutes give executive branch agencies the power to create regulations, which are published in the Federal Register and codified into the Code of Federal Regulations. Regulations generally also carry the force of law under the Chevron doctrine. Many lawsuits turn on the meaning of a federal statute or regulation, and judicial interpretations of such meaning carry legal force under the principle of stare decisis.

Answer: stare decisis


Question: Why should I use unit testing?, Context: Unit testing is a software development process that involves synchronized application of a broad spectrum of defect prevention and detection strategies in order to reduce software development risks, time, and costs. It is performed by the software developer or engineer during the construction phase of the software development lifecycle. Rather than replace traditional QA focuses, it augments it. Unit testing aims to eliminate construction errors before code is promoted to QA; this strategy is intended to increase the quality of the resulting software as well as the efficiency of the overall development and QA process.

Answer:
to reduce software development risks, time, and costs