Which among the following is the correct way to find out the index of second 's' in the string "She sold her beauty in one night to someone else"?

String a = "She sold her beauty in one night to someone else";
int i;
i = a.SecondIndexOf("s");

String a = "She sold her beauty in one night to someone else";
int i, j;
i = a.FirstIndexOf("s");
j = a.IndexOf("s", i + 1);

String a = "She sold her beauty in one night to someone else";
int i, j;
i = a.IndexOf("s");
j = a.IndexOf("s", i + 1);