$$A = \{ - 3 , - 2 , - 1,0,1,2,3 \}$$
All 2-element subsets of the set are written. The sum of the elements of each of these subsets is calculated separately and set B is formed with these numbers.
Accordingly, how many elements does set B have?\\
A) 9\\
B) 11\\
C) 13\\
D) 15\\
E) 17