A manufacturing plant produces custom hardware for specific applications in construction. One particular kind of bolt that is intended to have a length of 84mm is produced by two different machines, A and B. Tristan is an employee in the department that produces this bolt. He randomly selects samples of 100 bolts from each machine and measures the length of each one. The lengths of the bolts, in millimeters, are shown in the table below. Each machine produced a boltthat has a length of 84.05mm.

Use Excel to calculate each machine's z-score for producing a bolt that has a length of 84.05mm.