A certain pilot flew 400 miles to City K at an average…

A certain pilot flew 400 miles to City K at an average speed of 350 miles per hour with the wind and made the trip back at an average speed of 150 miles per hour against the wind. Which of the following is closest to the pilot’s average speed, in miles per hour, for the round-trip?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #14060