Answer:
1980
We can choose 2 men from 9 in 36 in ways.
We can choose 2 women from 11 in 55 ways.
For any arrangement of 2 men there are 55 ways of combining them with 2 women => 55 * 36 = 1980 total ways.
If you're wondering how i got the numbers i used the combination formula:
C(n, k) =
36. If 7/11 did bring one, then 4/11 didn't. 4*9=36
(4,5)(2,1)
slope = (1 - 5) / (2 - 4) = -4/-2 = 2
(-2,3)(-4,4)
slope = (4 - 3) / (-4 - (-2) = 1/(-4 + 2) = -1/2
2 and -1/2 are negative reciprocals of each other....therefore, ur lines are perpendicular <==