【Answer】Solution: According to the problem, $\triangle A E D \sim \triangle D F B$, so $\frac{\mathrm{AE}}{\mathrm{DF}}=\frac{\mathrm{DE}}{\mathrm{BF}}$. Since $A E=30$ cm, $B F=25$ cm, the area of rectangle DE \times DF = AE \times BF = 30 \times 25 = 750$ square cm. Therefore, the answer is 750.
14. (5 points) As shown in the figure, right triangle $ABC$ is composed of two right triangles, Jia and Yi, and a rectangle, Bing. $AE=30$ cm, $BF=25$ cm. What is the area of rectangle Bing in square centimeters? $\qquad$