Answer:
I would talk to my friend and try to come to an agreement so that he or she would pay half the repairs the sofa would need.
Explanation:
Although animals are unpredictable and my friend is not to blame for the damage his cat did to my sofa, the cat is my friend's responsibility, just as it was my responsibility to look at what the cat was doing and prevent him from destroying anything .
As we cannot charge the cat to pay for the damages it caused, the best option would be to enter into an agreement with my friend and ask him to pay half the repair that his cat caused.