Type the correct answer in the box. Use numerals instead of words. If necessary, use / for the fraction bar. This data set represents the number of cups of coffee sold in a café between 8 a. m. and 10 a. m. every day for 14 days.

{10, 9, 6, 12, 4, 6, 7, 8, 15, 14, 12, 9, 10, 5}.

The difference of the values of the first and third quartiles of the data set is
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The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?