You Want to Insert an Aluminum Rod, Which at 20°C

You want to insert an aluminum rod, which at 20°C has a radius of 1.00020 cm into a copper tube which has a radius of 1.00010 cm at the same temperature. You decide to put both of them in the refrigerator. At what temperature will the rod just fit if both are cooled to the same temperature? The coefficient of thermal expansion for aluminum is 2.4 × 10^-5K^-1, and that of copper is 1.7 × 10^-5K^-1.

A) 7.8°C
B) 6.3°C
C) 9.2°C
D) 14.7°C
E) 5.7°C