Which of the following is equivalent to the sum ∑k=1n(3k+2)\sum_{k=1}^{n} (3k+2)∑k=1n(3k+2)?
3n2+7n2\frac{3n^2+7n}{2}23n2+7n
3n2+5n2\frac{3n^2+5n}{2}23n2+5n
3n2+2n3n^2+2n3n2+2n
n2+3n2\frac{n^2+3n}{2}2n2+3n