AMC 10 2022b Problem 15

Let $S_n$ be the sum of the first $n$ term of an arithmetic sequence that has a common difference of $2$. The quotient $\frac{S_{3n}}{S_n}$ does not depend on $n$. What is $S_{20}$? $\textbf{(A) } 340 \textbf{(B) } 360 \textbf{(C) } 380 \textbf{(D) } 400 \textbf{(E) } 420$