In Question 4, does there exist an inertial reference frame moving along the x-axis whose observer might

Question:

In Question 4, does there exist an inertial reference frame moving along the x-axis whose observer might observe the two events at the same location? If so, what direction would that frame’s velocity have to be? Explain.
In Q Events A and B happen on your x-axis. They are separated by 500 m. You observe that A occurs 1.00μs before B. Could A have caused B? Explain.