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:



Answer:

Step-by-step explanation:
Answer:
All Tickets to one movie cost 
Step-by-step explanation:
Given:
Number of rows in theater = n
Number of seats in each row = m
Total number of seats in the theater = Number of rows in theater
Number of seats in each row= 
Now given each ticket costs = 
So to find total of all tickets we need multiply each ticket cost by Total number of seats in the theater
Total tickets cost = each ticket cost
Total number of seats in the theater = 