Answer:
13
Step-by-step explanation:
Amy can estimate with 10% instead, so she can just simply move the decimal point of $9.11 to the right, and so it will be estimated to more than 91 cents.
Use the next formula to find the margin or error:

z is the critical value (For a 95% confidence level the z-score is 1.95998)
σ is the standard deviation
n is the sample size

<h2>Then the margin of error is: 6.6639</h2>
The awnser is 20 quarters