The correct answer is: "when the high profits earned by producers cause a decrease in the welfare of other social actors".
A mixed market economy combines both aspects from pure market and centrally-planned economic systems.
In a mixed economy, producers and consumers interact in the markets and determine through their choices the prices and the amounts exchanged of the different products, services and factors of production. But market outcomes are not considered efficient or fair in many situations, this is why economic authorities have power to intervene in the functioning of markets in order to introduce income redistribution policies, for example.
The aim is to obtain the highest possible level of welfare for all economic agents who participate in the economy. If there are sharp inequalities, and the sucess of one economic agent (for example, producers) is hampering the possibilities of sucess of the others, the economic authorities will intervene.