$70 = 25 + 25 + 10 + 10$ 
Balloons are sold in packets of $$5$$, $$10$$, and $$25$$. Marius buys exactly $$70$$ balloons. What is the smallest number of packets he can buy? (2017 Math Kangaroo Problem, Level 3 - 4, Question \#11) 

a. $$3$$ 
b. $$4$$ 
c. $$5$$ 
d. $$6$$ 
e. $$7$$ 