Mark Shekhar Garg goes to a school to demonstrate how the kids can use the Facebook harmlessly and take the optimum advantage of socialization with fellow kids online at the early age of their social being. He tells the kids, after demonstrating the usage and safety features, that to make someone your facebook friend you have to send her/him a request and the other person has to accept it; as in out of two classmates $\mathrm{A}$ and $\mathrm{B}$ if first $\mathrm{A}$ sends request to $\mathrm{B}$ then $\mathrm{B}$ will accept it or if first $\mathrm{B}$ sends request to $\mathrm{A}$ then $\mathrm{A}$ will accept it and thus both $\mathrm{A}$ and $\mathrm{B}$ will become facebook friends.

As every kid responds to his instructions, within a minute Mark finds that every student in the class is now facebook friend of the other. In that class the number of female students is twice that of male students. He also notices that the number of friend-requests sent by the female kids is equal to the number of friend-requests sent by the male kids. Which of the following can be the number of friend-requests sent by female students to male students of that class?