We found this general rule:
If point P is positioned p units from the left edge of a table that is u wide and v high, then, if the ball starts along a line with slope v/(u–p), the ball will return to its starting position.
[For example, when P is positioned 6 units across a 9 by 6 table, a slope of 6/3 will be successful.]

Can you see why? How does this rule relate to any of your rules? Can we use the rule to find a desired position for B?

PPS: We show a related task involving an hexagonal table on the next page.