**Concept:** The question tests on the basics of Relative Speed(Rates)

**Solution:**

When 2 objects are in motion simultaneously, we use relative speed.

When objects are moving in the same direction, we subtract speeds.

Time = Distance / Relative Speed

relative Speed = (75 - 15) * 5/18 = 300/18 = 100/6 m/s

Time = 200 / (100 / 6) = 12 seconds**Option B**