My son's car was totaled and the insurance company offered us a very low price?

My son was rear ended at a high rate of speed. He was pushed 6 feet into the car in front of him. The guy had to really be moving when he hit my son. He was driving a 1999 Chevy Lumina LS. The blue book value according to NADA is $5000. It only had 78,000 miles onthe car. No rust on the body and overall in excellent shape. The insurance company offered me $3600 for the car. I can NOT find a replacement car in that shape for that price...