12) Tullio's library deposit is a cubic room with a side of $5 \mathrm{~m}$ and has recently become too small to hold all the warehouse stock. Therefore, Tullio bought a new one, also cubic, which, replacing the previous one, allowed him to gain $218 \mathrm{~m}^{3}$ of space. By how many meters is the side of the new deposit longer than the old one?
(A) $1 \mathrm{~m}$
(B) $2 \mathrm{~m}$
(C) $3 \mathrm{~m}$
(D) $4 \mathrm{~m}$
(E) $5 \mathrm{~m}$.
12) The answer is (B)

Indeed, the volume of the new tank is $(125+218) \mathrm{m}^{3}=343 \mathrm{~m}^{3}$, so the side will measure $\sqrt[3]{343} \mathrm{~m}=7 \mathrm{~m}$.