Question 78
Let $T$ be a triangulation of a convex 100-gon. We construct $P(T)$ by copying the same 100-gon and drawing a diagonal if it was not drawn in $T$, and there is a quadrilateral with this diagonal and two other vertices so that all its sides and the other diagonal are in $T$. Let $f(T)$ be the number of intersections of diagonals in $P(T)$. Find the minimum and maximum of $f(T)$.