It's North versus the South! Magazine A claims that there is no difference between mean incomes of citizens who live

in the Northern half of the USA and those who live in the Southern half of the USA. It is known that the population

standard deviation of incomes in the USA is $9,000. Magazine B claims that there is a difference. Magazine B randomly

surveys 250 Northerners and finds that the mean income is $79,000 with a standard deviation of $11,000. Magazine B

randomly surveys 320 Southerners and finds that the mean income is $76,000 with a standard deviation of $12,000.