How do you journalize the following entries?

A car was bought for $40,000 on loan. This was sold for the written down price of $15,000. The loan balance on books is $25,000.
He then buys a new car for $50,000. The loan is refinanced and the loan balance now is $50,000. In other words, the old balance of $25000 the new loan $25,000.

If the cost of new car is -
Car purchased cost $50,000 Dr
Car loan $50,000 Cr
What is the entry to close the $25,000 which is the old loan balance?