OD is the distance from the point of origin between the X and Y axes and the intersection of the D-curve with the X axis. The OD distance, is the distance on the diagram from the point of origin to number 120.-The Marginal Revenue (MR) MUST ALWAYS bisect the OD distance on the X-axis! (The MR bisects that distance at the value of 60). Why does this happen? Please see Elasticity Diagram at the top of the assignment description.