Answer:
Exact form : <u>10√11</u>
Step-by-step explanation:
The first step is to multiply the fraction by (3 +3i) / (3 +3i) to delete the i terms from the denominator:

Answer:



Step-by-step explanation:
Given

Solving (a): Point estimate of difference of mean
This is calculated as: 


Solving (b): 90% confidence interval
We have:


Confidence level is: 



Calculate 


The z score is:

The endpoints of the confidence level is:






Split


Hence, the 90% confidence interval is:

Solving (c): 95% confidence interval
We have:


Confidence level is: 



Calculate 


The z score is:

The endpoints of the confidence level is:






Split


Hence, the 95% confidence interval is:

The answer should be the last one D