Question 25
(MON 2) Given $k$ parallel lines and a few points on each of them, find the number of all possible triangles with vertices at these given points.
Source footnote 4. The problem is unclear. The correct formulation could be the following: Given $k$ parallel lines $l_1,\ldots,l_k$ and $n_i$ points on the line $l_i$, $i=1,2,\ldots,k$, find the maximum possible number of triangles with vertices at these points.
Source footnote 4. The problem is unclear. The correct formulation could be the following: Given $k$ parallel lines $l_1,\ldots,l_k$ and $n_i$ points on the line $l_i$, $i=1,2,\ldots,k$, find the maximum possible number of triangles with vertices at these points.