The average full-sized front loading energy star clothes washer uses 15 gallons of water per load. Assume that the population standard deviation for the number of gallons of water used to wash a load by these machines is 3.0.

Part A

What is the probability that a random sample of 90 loads washed in a full sized front loading energy star clothes washer will provide a sample mean gallons of water used that is within one-half gallon of the population mean of 15 gallons?

Part B

What is the probability that a random sample of 90 loads washed in a full size front loading energy star clothes washer will prvide a smaple mean gallons of water used that is at least three-quarters of a gallon greater than the population mean of 15 gallons.

Part C

What is the probability that a random sample of 75 loads washed in a full sized front loading energy stars clothes washer will provide a sample mean gallons of water used that is no more than one-quarter of a gallon less than the population mean of 15 gallons.

Please use the excel formula to work on it