有人帮我写一下mixed economic&free economic的定义,还有举例,优缺点,用英文写.

The United States' top monetary official says the country's economy continues to grow and create jobs,but is hindered by several factors,including negative developments in the housing industry.VOA's Michael Bowman reports from Washington,where Federal Reserve Chairman Ben Bernanke spoke at a hearing of Congress' Joint Economic Committee.
If legislators were looking for a clear-cut,decisive prediction on the future of the U.S.economy,they did not get it from Ben Bernanke.The U.S.central bank chief noted several positive trends that suggest further economic expansion,including rising exports and continued job creation.
"The continuing increases in employment,together with some pick-up in real wages,have helped sustain consumer spending,which increased at a brisk pace in the second half of last year,and has continued to be well maintained so far this year," he said.
"Growth in consumer spending should continue to support the economic expansion in coming quarters," he continued.
But Bernanke was quick to add that all is not well.In particular,he pointed to a dramatic slowdown in America's once-booming housing market,regarded as a primary engine of U.S.economic growth in recent years.
"To the downside,the correction in the housing market could turn out to be more severe than we currently expect,perhaps exacerbated by problems in the sub-prime sector," the Federal Reserve chairman said.
"Moreover,we could see yet greater spillover from the weakness in housing to employment and consumer spending than has occurred thus far," he added.
The "sub-prime sector" refers to mortgages held by roughly 10 percent of U.S.homeowners that often feature higher interest rates and sometimes allow a homeowner to pay only the interest on their loan,thereby accruing no equity.Such plans are generally offered to people with poor credit or low income levels.
Foreclosures in the sub-prime sector have skyrocketed in recent months,leading U.S.officials and legislators to question the lending practices of some financial institutions.
The Federal Reserve Board decides when and whether to raise or lower interest rates,based on its reading of current economic conditions and its projections of future ones.Many look to the Federal Reserve chairman as America's top economic prognosticator.