All three-element subsets of a four-element set A whose elements are integers are written out. When the arithmetic mean of the elements of each of these subsets is calculated, the values 8, 9, 10, and 11 are found.
Given this, which of the following is not an element of set A?\\
A) 5\\
B) 8\\
C) 11\\
D) 14\\
E) 17