The coordination problem in the centrally planned economies refers to the idea that

planners had to direct required inputs to each enterprise.
exports had to be equal to imports for a central plan to work.
the price level and the level of employment were inversely related.
the immediate effect of more investment was less consumption.

A centrally planned economy is also referred to as a communist economy or command economy. This is an economic system where decisions on what to produce, how to produce and for whom to produce are taken by central authority, such as a government.  Government makes economic decisions regarding the manufacturing and the distribution of products. For example; the economy of North Korea is a centrally planned system.

The coordination problem in the centrally planned economies refers to the idea that planners had to direct required inputs to each enterprise.

answer; (a) calling people who have not shown interest in the product and asking them to buy it;