这题怎么做？---**Extraction Content:**
**Question Stem:**
7. 为倡导低碳生活, 绿色出行, 某电动车俱乐部利用周末组织“远游”活动, 电动车队从甲地出发骑向乙地, 1.5小时后, 恰有一辆邮政车从甲地出发, 沿电动车队行进路线前往乙地, 如图是电动车队离甲地的路程y(km)与电动车队离开甲地时间x(h)的函数关系图象; 请根据图象解答下列问题
**Sub-questions:**
(1)邮政车到达乙地后, 电动车距乙地多少千米?
(2)求线段CD对应的函数关系式;
(3)邮政车到达乙地后, 马上沿原路以与CD段相同的速度返回, 求邮政车从甲地出发后多长时间再次与电动车相遇.
**Chart/Diagram Description:**
* **Type:** Line chart (distance-time graph).
* **Main Elements:**
* **Coordinate Axes:** X-axis represents time (x), labeled "x(h)". Y-axis represents distance from place A (y), labeled "y(km)". The origin O is at (0, 0).
* **Lines/Segments:** There are two primary paths shown. The line segment OA represents the journey of the electric vehicle team. The line segment CD represents a portion of the journey of the postal vehicle.
* **Points:**
* O: (0, 0) - Represents place A at time 0.
* A: (5.5, 300) - Represents the electric vehicle team reaching place B (300 km from A) at time 5.5 hours.
* C: (2.5, 60) - Represents the postal vehicle's position (60 km from A) at time 2.5 hours (since the electric vehicle left A).
* D: (4.5, 300) - Represents the postal vehicle reaching place B (300 km from A) at time 4.5 hours (since the electric vehicle left A).
* B: Labeled on the X-axis at 1.5. According to the text, the postal vehicle starts 1.5 hours after the electric vehicle. This label might indicate the starting time of the postal vehicle (x=1.5h).
* **Labels and Annotations:** Specific x-axis values are marked near points B, C, D, A as 1.5, 2.5, 4.5, 5.5 respectively. Y-axis is scaled with major ticks at 60, 120, 180, 240, 300. The graph shows dashed lines from points A and D to their respective axes to indicate their coordinates. The labels "y(km)" and "x(h)" are on the Y and X axes respectively. The origin is labeled "o".
**Other Relevant Text:**
The problem states that the postal vehicle departs from place A 1.5 hours *after* the electric vehicle team departs. The graph shows the distance from place A y(km) versus the time since the electric vehicle team left place A x(h). Place B is the destination. Based on the graph, place B is 300 km from place A (both the electric vehicle and the postal vehicle reach y=300).
Based on the graph and text:
- Electric vehicle travels from A to B: from (0,0) to (5.5, 300). Distance AB = 300 km. Time taken by electric vehicle = 5.5 h.
- Postal vehicle starts at x=1.5h from A (y=0 at x=1.5 is implied by the text, though the graph of the postal vehicle shown as CD starts later). The segment CD represents the postal vehicle's journey from C(2.5, 60) to D(4.5, 300). The postal vehicle reaches B (y=300) at x=4.5h.
**Calculations derived from the graph for context (not explicitly requested in output, but needed to answer questions):**
- Speed of electric vehicle: (300-0) / (5.5-0) = 300 / 5.5 = 600/11 km/h.
- Speed of postal vehicle along segment CD: (300-60) / (4.5-2.5) = 240 / 2 = 120 km/h.