Consider the sequence ana_nan defined by an+1=an+da_{n+1} = a_n + dan+1=an+d. If limn→∞Snn2=5\lim_{n \to \infty} \frac{S_n}{n^2} = 5limn→∞n2Sn=5, what is the common difference ddd?
555
101010
2.52.52.5
202020