820.9 million km thats your answer
Answer:

Explanation:
L = Initial length of segment = 79 m
T = Normal temperature = 
l = Width to be left for expansion
= Coefficient of linear expansion of the material = 
= Maximum temperature = 
= Change in temperature = 
The expression of linear expansion is given by

The expression for the minimum gap distance l the engineers must leave for a track rated at temperature
is 
Use the conservation of momentum formula: m1v1 + m2v2 = v(m1 + m2)
(0.005kg)(250m/s) + (12kg)(0m/s) = v(0.005kg + 12kg)
v = ((0.005kg)(250m/s)) / (0.005kg + 12kg)
v = 0.104 m/s
The triangle stands for change. X means the distance spring stretched or compressed. so together, it's the change in the distance of the spring stretched or compressed.