JSON

Carefully study the JSON object below and specify which line contains an error:

{  
  persons: [  
    {  
      "firstName": "Stanislaw",
      "lastName": "Lem",
      "book": [  
        {  
          "title": "Summa Technologiae",
          "year": 1964
        }
      ]
    },
    {  
      "firstName": "Isaac",
      "lastName": "Asimov",
      "book": [  
        {  
          "title": "The End of Eternity",
          "year": 1955
        }
      ]
    }
  ]
}

Write the line number as the answer.

If you try your best but you don't succeed, you can search the JSON validators — special services that check the correctness of the code.