please explain

\fTM: The .Internal Revenue Service reports that the. mean federal income tax paid in the-year 2010 was $3040. Assume that the _ standard deviation is $4500. The IRS plans to draw a sample of 1000 tax returns to study' the effect of a new tax law. (aj What is the probabity that the sample mean tax is less than $8000? Round the answer to at least four decimal places. The probabity that the sample mean. tax is less than $8000 is D . (b) What is the probabity that the sample mean tax is between $7400 and $8000? Round the answer to at least four. decimal places. ' The probabity that the sample mean. tax is between $7400 and $8000 is D . (c) nd the 60th percentie of the sample mEan. R0und the answer to at least two decimal places. The 60'\"l percentie of the sample mean is SD