When Graphing the Amount of Resources a Parent Invests in a Focal

When graphing the amount of resources a parent invests in a focal offspring against fitness costs to the parent and benefits to the offspring, what is the so-called zone of conflict?

A) where parent-offspring conflict takes place
B) where parents and offspring both benefit from decreasing allocation to the focal offspring
C) where parents and offspring both benefit from increasing allocation to the focal offspring
D) where b - c is maximized