What is the burden of proving reasonable diligence under discovery rule?

The party that seeks application of the discovery rule also has the burden of proving the exercise of reasonable diligence. Id. The issue is not what was actually known by the injured party "but what he might have known by exercising the diligence required by law," taking into account the "qualities of attention, knowledge intelligence and judgment which society requires of its members for the protection of their own interest and the interest of others." Nicolaou v. Martin , 649 Pa. 227, 195 A.3d 880, 893 (2018) (citation omitted).