1. (10 points) Evaluate the value of the ratio of numbers $A$ and $B$, if

$$
\begin{aligned}
& A=1 \cdot 2 \cdot 7+2 \cdot 4 \cdot 14+3 \cdot 6 \cdot 21+4 \cdot 8 \cdot 28 \\
& B=1 \cdot 3 \cdot 5+2 \cdot 6 \cdot 10+3 \cdot 9 \cdot 15+4 \cdot 12 \cdot 20
\end{aligned}
$$

a) $0<A / B<1$;

b) $1<A / B<10$;

c) $10<A / B<100$;

d) none of the listed answers is correct.

Select the correct answer, no need to provide the solution.
Answer: a).

Solution. It is not hard to see that in both number $A$ and number $B$, the second term is twice the first, the third is three times, and the fourth is four times. Thus, the ratio of $A$ to $B$ is equal to the ratio of their first terms. This ratio is $\frac{14}{15}$, which is less than 1.