4. A traffic accident witness said that the license plate number contains the letters RLH, followed by 3 digits and the first digit being 5. If the witness does not remember the last 2 digits but is...

Extracted text: 4. A traffic accident witness said that the license plate number contains the letters RLH, followed by 3 digits and the first digit being 5. If the witness does not remember the last 2 digits but is sure that the 3 digits are different, find the maximum number of car registrations the police will have to check.