Step-by-step explanation:

 
        
             
        
        
        
Answer:  
Step-by-step explanation:
As per given , we have
n = 11

Since population standard deviation is missing, so we use t-test.
Critical t-value for 99% confidence :
 [using two-tailed t-value table]
   [using two-tailed t-value table]
Confidence interval :

Hence,  99% confidence interval for the mean amount of time that students spend in the shower each day.= 
 
        
             
        
        
        
Answer:
8h + 15 = 39
Step-by-step explanation:
The base fee is 15 so you shouldn't multiply the hours by it. 
The question states 8 per hour which means that you should multiply the 8 by hours and add on the base fee which is 15. 
 
        
                    
             
        
        
        
Answer:
9 1/6
You may use a fraction calulator for this question by the way!
Hope this helps!
Sorry if its wrong!
Have a nice day!