Answer:
(22.12, 27.48)
Step-by-step explanation:
Given : Significance level : 
Sample size : n= 8 , which is a small sample (n<30), so we use t-test.
Critical values using t-distribution: 
Sample mean : 
Standard deviation : 
The confidence interval for population means is given by :-

i.e. 

Hence, the 95% confidence interval, assuming the times are normally distributed.= (22.12, 27.48)
The smallest value is $0.25 (a quarter) because you can use two quarters and a half dollar. Only one of them can't be a half dollar, but the other two can be.
4/15
Multiple the numerator by numerator, and denominator by denominator, then simplify
Looking at the graph, trace your finger up from 10 on the x-axis. You will end up somewhere around 17.
Therefore, the approximate height of the tree after 10 years will be 17 feet.