examday

/TMUA

Let $A_1,A_2,A_3$ be three points on a straight line. Let $B_1,B_2,B_3,B_4,B_5$ be five points on a straight line parallel to the first one. Each of the three points on the first line is joined by a straight line to each of the five points on the second line. Further, no three or more of these joining lines meet at a point except possibly at the A's or the B's. Then the number of points of intersections of the joining lines lying between the two given straight lines is