Pleas solve it in excel with formulas showing.

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A manufacturer of disk drives for notebook computers wants an MTBF of at least 45,000 hours. Recent test esults for 10 units were one failure at 10,000 hours, another at 25,000 hours, and two more at 45,000 hours. The remaining units were still running at 50,000 hours. Determine the following: a) Percent of failures ) Number of failures per unit-hour E) MTBF at this point in the testing