2021 AMC 12A Problem 20

Suppose that on a parabola with vertex V and a focus F there exists a point A such that AF=20 and AV=21. What is the sum of all possible values of the length FV?

\textbf{(A) }13 \qquad \textbf{(B) }\frac{40}3 \qquad \textbf{(C) }\frac{41}3 \qquad \textbf{(D) }14\qquad \textbf{(E) }\frac{43}3

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.