32・15 In the following equation, each letter represents a different digit in the decimal system, $(Y E) \cdot(M E)=T T T$, in the left product $Y E$ is smaller than $M E$. Then the sum of $E+$ $M+T+Y$ is 
(A) 19.
(B) 20.
(C) 21.
(D) 22.
(E) 24.
(24th American High School Mathematics Examination, 1973)
[Solution] Given $T T T=T \cdot(111)=T \cdot 3 \cdot 37$, and $T$ equals the last digit of $E^{2}$. Since $M E > Y E$, $M E$ must include the factor 37, so it could be 37 or 74.

The latter possibility is ruled out, because in this case the smallest possible $Y E=14$, resulting in $14 \cdot 74=1036$, which exceeds $999=$ TTT.
Thus, $M E=37$, and since $Y E=Y 7$ must be divisible by 3, it is 27.
Therefore, $27 \cdot 37=999$.
Hence, the sum sought is $E+M+T+Y=7+3+9+2=21$.

Therefore, the answer is $(C)$.