Relation between z-scores and percentiles; Chebyshevs theorem)

Suppose you have a sample of data for a particular variable. Within this sample, there is a particular observation, say XWithin the sample, what is the maximum possible percentile that that has a z-score of 2.85.could represent? In other words: Suppose you had accessto this sample data, and that you then could calculate which percentile Xrepresents within the data. What is the maximumpossible percentile that Xcould be?