Generally speaking a mixed economy is one where the government has controls over private industry through various types of regulations. One example is the setting of the minimum wage. For the most part a mixed economy does not require the government to actually own any of the means of production. Also, a mixed economy creates "authorities" to operate tunnels, bridges and airports.
The Federal Reserve can change the money supply with 1) open market operations, 2)making changes in the reserve ratio, and 3) making changes in the discount rate. Of the three policies the open market is the most common.
business cycles
Board of Governors
A unitary-elastic supply indicates a good with a supply-price elasticity of one, which means that a 1% change in price increases supply by 1%.