A brass lid screws tightly onto a glass jar at 20oc to help

Question

Calculate the right answer of the following question

Question- A brass lid screws tightly onto a glass jar at 20^oC. To help open the jar, it can be placed into a bath of hot water. After this treatment, the temperatures of the lid and the jar are both 45^oC. The inside diameter of the lid is 7.5cm at 20^oC.

Part 1- Find the size of the gap (difference in radius) that develops by this procedure.

I need assistance to compute the size of the gap that develops by the procedure.