This data set represents the number of cups of coffee sold in a caf_ 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

Put numbers in order: 4,5,6,6,7,8,9,9,10,10,12,12,14,15

Cut the list into two equal parts: 4,5,6,6,7,8,9 and 9,10,10,12,12,14,15

Find middle numbers: 4,5,6,6,7,8,9 and 9,10,10,12,12,14,15

Lower quartile: 6
Upper quartile: 12

The difference of the values of the first and third quartiles of the data set is 12 - 6 = 6

The answer is the third choice