A girl named Heather uses a beaker to fill up parts of jars

A girl named Heather uses a beaker to fill up parts of jars so that on average ounces are contained in each jar. Heather wants the exact ounces per jar to be within 1 ounce of the mean for at least 79% of the time. What is the largest value of so that heathers objectives are met? The shape of the distribution is not given. Please show all your work I want to know how to do problems like these not just the answer

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