maximum is 6+6+6 = 18. 
Kevin has 3 regular dice. Each dice has numbers from 1 to 6. Which of the following could not be the sum of the numbers on top of the 3 dice? 

a. $$5$$ 
b. $$13$$ 
c. $$17$$ 
d. $$22$$ 
e. All the above numbers are possible sum 