Astronaut Mark Uri Is Space-Travelling from Planet X to Planet

Multiple Choice

Astronaut Mark Uri is space-travelling from planet X to planet Y at a speed of 0.65 c.When he is precisely halfway between the planets,a distance of 1 light-hour from each,nuclear devices are detonated.The explosions are simultaneous in Mark's frame.What is the difference in time of arrival of the flashes from the explosions as observed by Mark?

A) 0 min
B) 180 min
C) 90 min
D) 360 min