Final answer:
The plane's final position relative to Dallas is 270 km North after flying 400 km North and then 130 km South.
Step-by-step explanation:
The plane's final position relative to Dallas can be determined by subtracting the southward distance from the northward distance. The aircraft took off and flew 400 km north, then landed, refueled, and flew another 130 km south. To find the final position, we calculate 400 km North - 130 km South, which equals 270 km North of Dallas. Therefore, the correct answer to the student's question is 270 km North of Dallas.