The monthly sales (in thousands of $) at a certain restaurant for the past two years are given in the chart below:

Last Year: 9, 9.5, 10, 10, 11, 11, 11, 11, 11, 12.5, 13, 13
This Year: 9, X, 10, 10, 11, 11, 11, 11, 11, Y, 13, 13

If the standard deviation of the monthly sales is greater this year than last year, which of the following are possible values for X and Y?

A) 9 and 12.5
B) 10 and 11
C) 10 and 12.5
D) 11 and 11
E) 11 and 12.5


OA A

Source: Manhattan Prep