Consider the set of 30 parabolas defined as follows: all parabolas have as focus the point (0,0) and the directrix lines have the form y=a x+b with a and b integers such that a \in\{-2,-1,0,1,2\} and b \in\{-3,-2,-1,1,2,3\}. No three of these parabolas have a common point. How many points in the plane are on two of these parabolas?
Answer Choices
A. 720
B. 760
C. 810
D. 840
E. 870