we are given
The ez pay plan costs $0.15 per minute
so, cost is $0.15 per minutes
we have
x minutes on the ez pay plan
so, time for plan is x minutes
total bill = cost * time for plan
now, we can plug values
we get
total bill = $0.15x..............Answer
We cannot calculate the confidence interval without the sample size. However, for the second question, the sample size needed would be 49.
The formula we use is

To find the z-score:
Convert 98% to a decimal: 0.98
Subtract from 1: 1-0.98 = 0.02
Divide by 2: 0.02/2 = 0.01
Subtract from 1: 1-0.01 = 0.99
Using a z-table (http://www.z-table.com) we see that this value is closest to a z-score of 2.33.
Using the z-score, our standard deviation (9) and our margin of error (3), we have:
If you were to reflect them, the answer would be the same numbers with the opposite sign. Therefore, the answer should be (2,-6) hope that helped!!!!