Replacing x with x + 4 increases the total sum by exactly 4.

Original average = 52, so original total = 52n.
New total = 52n + 4.
New average = (52n + 4) ÷ n = 53.7.

52n + 4 = 53.7n.
4 = 1.7n.
n = 4 ÷ 1.7 = 40 ÷ 17 ≈ 2.35.

n is not an integer. The numbers in the question may be transcribed incorrectly — check the original source. If the average rise were 0.2 (instead of 1.7), then n = 4÷0.2 = 20, matching option C.

Final Answer: n is approximately 2.35 (not an integer — likely a question error)