Answer:
Consider frames X and Y:
If X sees Y moving to his right then Y must see X moving to his right.
If this is not true then one can choose one frame over the other ( a favored frame and this is not allowed)
The car heads east at an average speed of 50 miles per hour from the intersection point towards East. The truck heads east at an average speed of 60 miles per hour from the intersection point towards South.
The distance of car from the intersection point after t hours is
.
The distance of truck from the intersection point after t hours is
.
Since these distances are perpendicular to each other, distance apart d (in miles) at the end of t hours is

Thus the distance apart is 
The answer is (a) because movement is acceleration
The universe is 13.8 billion years old.