If range is less than 9, then the difference between the largest and teh smallest members of the set should be ,9

The difference of all the given numbers < 9

So even if we were to assume that the difference between x and y is less than 18

then let us try to find values of x and y

So x = 7 + 10 = 17

y can be the same as well = 7 + 10 = 17

So x + y can be > 18,

Again, x+y can be any other numbers as 1 and 2, and the range is still < 9.

so (1) is not sufficient.

From (2)

(x+y)/2 < (7 + y + 12 + 8 + x + 9)/6

=> 6(x+y) < 2(x+y + 36)

=> 4(x+y) < 2*36

=> (x+y) < 18

So Answer - B

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