A total of m different points are selected on a particular line, and a total of n different points are selected on another line parallel to the first, where each of m and n is greater than 1. In how many different ways can a triangle be made with its vertices at three of the selected points?
Choose the correct choice from the following choices:  A) m^2n+mn^2  B) mn(m+n-2)  C) mn(m+n−2)/2  D) (m+n)(m+n−1)(m+n−2)/6  E) (m+n)!/m!n!
ase 1: One point on particular line and other 2 points on parallel line. #ways=   m* nc2   Case 2: one point on parallel line and other 2 on particular line.   n* mc2   Total   m* nc2+ n* mc2   mn(m+n-2)   ANS:mn(m+n-2)
<result>B</result>
A total of m different points are selected on a particular line, and a total of n different points are selected on another line parallel to the first, where each of m and n is greater than 1. In how many different ways can a triangle be made with its vertices at three of the selected points?