Answer:
a) 
With:


b) 

c) 

d) 


Step-by-step explanation:
For this case we know the following propoertis for the random variable X

We select a sample size of n = 81
Part a
Since the sample size is large enough we can use the central limit distribution and the distribution for the sampel mean on this case would be:

With:


Part b
We want this probability:

We can use the z score formula given by:

And if we find the z score for 89 we got:


Part c

We can use the z score formula given by:

And if we find the z score for 75.65 we got:


Part d
We want this probability:

We find the z scores:



<u>Given</u>:
Four lines are marked proportion, the length of TW can be determined by

<u>Value of a:</u>
Let us set the proportion for the given lines.
Thus, we have;



Thus, the value of a is 5.6
<u>Value of b:</u>
Let us set the proportion for the given lines.
Thus, we have;



Thus, the value of b is 5.
<u>Length of TW:</u>
The length of TW is given by


Thus, the length of TW is 13.6
I’m not sure just need to answer questions to help me so sorry
Answer
10.5
Step-by-step explanation:
Answer;
7.77
Step-by-step explanation: