Permutation/Combinations question

[jsl]

L1 and L2 are two parallel lines in a plane. If L1 has 6 points equally spaced along its length and if L2 has 5 points also equally spaced along its length, how many different triangles can be formed by connecting the points on the two parallel lines?

135
90
60
30
15

[earth@work]

IMO A
Taking line L1, total triangles= 6x5C2 = 60 ways
Taking line L2, total triangles = 5x6C2 = 75 ways
Total = 60 +75 = 135 ways
what is the OA

[stop@800]

yup, has to be A
6c2 * 5c1 + 6c1 * 5c2

135

[jsl]

OA: A

Thanks