Find number abc

A woman took her dog to the vet. She said, "I think my dog is dead". The doctor laid the dog on the table and reached down and took a cat out of a box. The cat walked all over the dog and the dog didn't move. "Yes, your dog is dead," says the doctor.
"How much do I owe you?" the lady asks.
"$345," says the doctor.
"$345!!?" the lady asks.
"Yes. $45 for the office visit and $300 for the cat scan."