The Internal Revenue Service reports that the mean federal income tax paid in the year 2010 was $8040. Assume that the standard deviation is $4800. The IRS plans to draw a sample of 1000 tax returns to study the effect of a new tax law.

What is the probability that the sample mean tax is less than $8200? Round the answer to at least four decimal places.

What is the probability that the sample mean tax is between $7400 and $7900? Round the answer to at least four decimal places.

Find the 20th percentile of the sample mean. Round the answer to at least one decimal place.

Would it be unusual if the sample mean were less than $7700? Round the answer to at least four decimal places.