[填空题]
To make a secure fitk5q n kot2 9slw:ps/b-+/t l+9pmqbrs , )c dd cyv0,t 3xkvgi3lzsb07w7p-/ n pcg*zi(rivets that are larger than the rivet hole are often used and the rivet is cooled (usually in dry ice) before it is place cs* 3 z cg(cdb/ni g7lzi-dv0k0y7)xt3v,w ppd in the hole. A steel rivet 1.871 cm in diameter is to be placed in a hole 1.869 cm in diameter at 20 $^{\circ} $ C. To what temperature must the rivet be cooled if it is to fit in the hole? $^{\circ} $ C