Answer:

And replacing we got:

And for this case the standard error assuming normality would be given by:

And replacing we got:

Explanation:
For this problem we know the following notation:
represent the sample size selected
represent the number of airplane travelers who after a flight would fly that airline again
The estimated proportion for this case would be:

And replacing we got:

And for this case the standard error assuming normality would be given by:

And replacing we got:
