Using the z-distribution, as we are working with a proportion, it is found that the margin of error for the 90% confidence interval is of 0.0524 = 5.24%.
<h3>What is a confidence interval of proportions?</h3>
A confidence interval of proportions is given by:

In which:
is the sample proportion.
The margin of error is given by:

In this problem, the critical value is given as z = 1.645, and since 26 out of 80 students said they would be willing to pay extra:

Then, the <em>margin of error</em> is of:

More can be learned about the z-distribution at brainly.com/question/25890103
Answer: they can buy about 8 dvds
Step-by-step explanation:
this is because 30 + 66 = 96 and if you do 96 divided by 12 it gives you 8
The number of pounds of copper in 120 pounds of brass is = 78 pounds of copper
<h3>Calculation of number of pounds of copper</h3>
The percentage of copper in the brass = 65%
Therefore the quantity of copper in the brass = 65/100= 0.65 pounds
This means that 1 pound brass contains = 0.65 pounds of copper
The quantity of copper in 120 pounds of brass = 120 * 0.65
= 78 pounds of copper.
Learn more about copper here:
brainly.com/question/24856041
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Answer: $4850
Step-by-step explanation:
The other information related to the question is:
Direct materials = $3.50
Direct labor = $1.10
Variable overhead = $0.45
Fixed overhead = $2.80
Total = $7.85
Based on the information given in the question, the increase in the profit will be calculated as the contribution from the 3000 extra units minus the worker's salary.
Contribution from 3000 units will be:
= (Selling price - Direct materials - Direct labor - Variable overhead) × 3000
= ($25 - $3.50 - $1.10 - $0.45) × 3000
= $19.95 × 3000
= $59850
Increase on Profit:
= $59850 - $55000
= $4850
A withdrawal of $50 is negative because you are taking money out of your account and your money in your account is getting less than what it was before.