Question 1: The temperature in January is estimated to have a mean of 34 and a standard deviation of 6, in degrees Fahrenheit. Sally estimates that her heating bill can be predicted using the following formula:
X = 300 - 5 × temp,
Where temp is temperature. Find how much she is expected to pay in January. Moreover, obtain the variance and standard deviation of the heating bill.
Question 2: An instructor graded a large number of midterm exams and she considers that the test scores are normally distributed with a mean of 70 and a standard deviation of 10.
(a) What is the portion of students obtaining scores between 85 and 95?
(b) What is the score needed to be at the top 10% of the class?