Question 24
The International Article Number has 13 digits ABCDEFGHIJKLM. Here M is a check digit. Let $S=A+3B+C+3D+E+3F+G+3H+I+3J+K+3L$ . If S is a multiple of 10, then M is chosen to be 0. Otherwise it is chosen to be $M=10-t$ where t is the remainder obtained when S is divided by 10. The Code for a certain Article Number is 6901020□09017. What is the missing digit?
