One observer stand on a train moving at a constant speed, and one observer stands at rest on the ground. The person on the train stands at the back of the car and turns on a flashight; the light travels to the front of the car, bounces off a mirror, and returns to the back of the car (assume the light is traveling in a vacuum). the observer on the train measures the time it takes for the light to take this path and knowing the length of the car, calculates the speed of light. What value does he obtain?

a) Greater than c

b) Equal to c

c) Less than c

d) The speed of the light canot be determined without knowing the speed of the train