A copper washer is to be fit in place over a steel bolt?

A copper washer is to be fit in place over a steel bolt. Both pieces of metal are at 15.0�C. If the diameter of the bolt is b = 1.0000 cm and the inner diameter of the washer is a = 0.9980 cm, to what temperature must the washer be raised so it will fit over the bolt? Only the copper washer is heated.