A1. The number $M$ consists of 2007 ones written consecutively, $M=111 \cdots 111$.

What is the sum of the digits of the number you get when you multiply $M$ by 2007?
(A) 2007
(B) 18036
(C) 18063
(D) 18084
(E) 4028049
A1. If $M$ consists of four ones, then $2007 \times M=2229777$, so the sum of the digits is $3 \times(2+7)+9=4 \times 9$. If $M$ consists of five ones, then $2007 \times M=22299777$; the sum of the digits is then $3 \times(2+7)+9+9=5 \times 9$. If $M$ consists of 2007 ones, then the sum of the digits is $2007 \times 9=18063$. (C).