这是天津中考第17题，请解答这道题目。视频开头是：大家好，今天来分析一下天津2025年中考第17题。第二问在以建系法解答时，要以B为原点，按照题目的图走。---**Extracted Content:** **(17) 如图，在矩形 ABCD 中，AB = 2，BC = 3，点 E 在边 BC 上，且 EC = 2BE。** **(I) 线段 AE 的长为______；** **(II) F 为 CD 的中点，M 为 AF 的中点，N 为 EF 上一点，若∠FMN = 75°，则线段 MN 的长为______。** **Diagram Description:** * **Type:** Geometric figure (rectangle with internal lines). * **Main Elements:** * **Shape:** A rectangle labeled ABCD. Vertex A is in the top-left, B is in the bottom-left, C is in the bottom-right, and D is in the top-right. * **Points:** Points A, B, C, D are vertices of the rectangle. Point E is located on the side BC, appearing closer to B. Point F is located on the side CD, appearing to be the midpoint. Point M is located on the line segment AF, appearing to be the midpoint. Point N is located on the line segment EF. * **Lines:** The sides of the rectangle AB, BC, CD, and AD are shown. Internal line segments AE, AF, EF, and MN are drawn. * **Labels:** Vertices A, B, C, D are labeled. Points E, F, M, N are labeled. * **Relative Position:** E is on BC. F is on CD. M is on AF. N is on EF. * **Caption:** The figure is labeled "第 (17) 题" (Question (17)).