<h2>Answer with explanation:</h2>
As per given , we have
Sample size : n= 5
Degree pf freedom = : df= 5-1=4
Significance level for 90% confidence =
Using t-value table , t-critical value for 90% confidence:
Margin of error of :
Interpretation : The repair cost will be within $12.39 of the real population mean value 90% of the time.