Tony Is Supervising a Work Crew at the Post Office

Tony is supervising a work crew at the post office. Every day, his clients are supposed to check each waste bin and empty those that contain trash. Tony takes data on the number of waste bins emptied by the crew. In order to report data in terms of percentage of occurrence Tony MUST also know:

A) that some waste bins contained trash.
B) how many waste bins contained trash.
C) how many waste bins were in the office.
D) This behavior is not amenable to percent of occurrence reporting.