We are given the following information
Investment = $5200
Annual interest rate = 4.2% = 0.042
Final amount = $16,500
Number of years = 27.7 years
Number of compoudings = quartely = 4
The student uses the following model

The general formula for compound interest is given by

As you can see, the number of compoundings is incorrect (3 vs 4)
The interest rate is also incorrect.
Let us substitute the given values into the above formula

Therefore, the final amount is approximately $16,543.5
Median: 29
Range: 25
IQR: 14.5
Explanations:
**Median:**
(To find the median, we need to first order all the elements)
Ordered —> 15, 18, 18, 20, 23, 28, 30, 33, 33, 34, 38, 40
(Since there are an even number of elements, we need to add the two elements in the middle and divide by 2)
Median = (28 + 30)/2 = 58/2 = 29
**Range:**
(To find the range, you just have the subtract the smallest one from the largest)
Range = 40 - 15 = 25
**IQR:**
First half of elements —> 15, 18, 18, 20, 23, 28
Second half of elements —> 30, 33, 33, 34, 38, 40
Q1 (Quartile 1) = Median of first half = (18 + 20)/2 = 38/2 = 19
Q3 (Quartile 3) = Median of second half = (33 + 34)/2 = 67/2 = 33.5
IQR = Q3 - Q1 = 33.5 - 19 = 14.5