An economic system that operates mainly on private transactions where firms are free to make their own production, distribution and pricing decisions is known as.

In Market economy individuals and firms are free to make their own choices. There is no regulatory authority that is monitoring the system. Firms can produce whatever they want and sell it at whatever price they desire. This idea of free market was first suggested by economist Adam Smith. Firms will only manufacture goods that market demands, even if they are dangerous to the society e.g. cannabis and LSD. If the demand exists and firms can make profit, they will produce it regardless of its impact on the society.
Command economy is heavily monitored by government. Government decide what to produce, how much to product and for whom to produce. The price is fix for every product. For example, if the price of cheese is set at $10 per pound, everyone will get it for $10. There is no concept of private ownership and everything is owned by the government.
Mixed economy, also known as traditional economy is a combination of above two types. There is private as well as public ownership. Firms can produce goods, but they will follow laws and regulations (firms can't make and sell LSD to teenagers). The government provide healthcare, education and protect consumers from private institutions.

The question deals with a situation where there is no government intervention. The firms are free to make their own production, distribution and pricing decisions. Hence, it’s a market economy.