IKMC 2020 - Grades 11-12 - Brazil Second Application - Self-study Question 10

In the shown addition CAN+GUR=UUU, different letters stand for distinct decimal digits and leading digits are nonzero. What is the largest possible C+A+N?



Source defect: the true maximum is absent from the printed options. Give the numerical maximum.

Printed choices: A. 15; B. 18; C. 19; D. 21; E. 24