Question

2) The amount of gasoline sold every week at a gas station is Normally distributed with a mean of 30,000 gallons and a Standard Deviation of 3,000 gallons. What is the Probability that in a given week that the amount of gasoline sold is between 28,000 and 35,000 gallons?

Answer 1

28000 is 0.666 std below the mean
35000 is 2.666 std above the mean.

Now go to your Z table. Or, you can play around with this stuff at

http://davidmlane.com/hyperstat/z_table.html