Just as for $$3\times7$$, $$33\times77$$, and $$333\times777$$, the first digit is a $$2$$, the last digit is a $$1$$, and the sum is $$2+1=3$$. 
If I multiply $$333333333333333$$ by $$777777777777777$$ and add the first and last digits of the product, the sum is． 
(A) $$3$$ 
(B) $$5$$ 
(C) $$7$$ 
(D) $$11$$ 