$3+7+2+8+1$  $=(3+7)+(2+8)+1$  $=10+10+1$  $=21$ 
What is the sum: $$3+7+2+8+1=?$$ (2007 Math Kangaroo Problem, Level 1-2, Question \#17) 
Options:
1: $$12$$ 
2: $$14$$ 
3: $$17$$ 
4: $$21$$ 
5: $$27$$ 