Counterfeit money exchanged by his own grandson

An old man took 40,000 yuan to the doctor, but it was changed into counterfeit money by his own grandson. Except for the first and last pieces of each pile of money, which were genuine, the remaining 392 pieces were counterfeit.一位老人拿4万元钱去看病，但是被自己孙子换成了假币。除了每沓钱的第一张和最后一张是真钱，其余392张都是假币。