A Rod Has a Length 2

A rod has a length 2.0000 m at 20.0°C. The length of the rod increases to 2.0005 m when the temperature increases to 40.0°C. What is the coefficient of thermal expansion of the material from which the rod is made?

A) 2.00 × 10^-5/K
B) 2.50 × 10^-5/K
C) 1.25 × 10^-5/K
D) 5.00 × 10^-3/K
E) 5.00 × 10^-5/K