Sum $$=$$ Middle Term $$\times$$ Number of Terms, $$20 \times 13 = 260$$. 
In an arithmetic sequence with $$13$$ terms, if the seventh term is $$20$$, what is the sum of all the terms? 

(1) $130 
(2) $$260$$ 
(3) $$300$$ 
(4) $$360$$ 