3. Given in $\triangle A B C$, $\angle A \leqslant \angle C \leqslant \angle B$, and $2 \angle B$ $=5 \angle A$. Then the range of $\angle B$ is $\qquad$ .
3. $75^{\circ} \leqslant \angle B \leqslant 100^{\circ}$