Who answers the three economic questions in a market economy? How is this different from command economy?

Market economies are characterized by their free markets. Examples are the United States and the United Kingdom.

Command economies are characterized by their control of markets. Examples are China and North Korea.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

its first and third is your answer i did the qustion the fourth isnt right