Change value of an item in Tjsonobject - Pascal

Question

I have the following code :

uses
Classes, SysUtils, CustApp, fpjson, jsonparser ;

var  
jsonEx4 : TJSONObject;
begin
  //Inicio do Exercicio 4
  jsonEx4:=TJSONObject.Create([
    'TProposta', TJSONObject.Create([
      'Ativo', '',
      'DiaVencimento', '0'
    ]),
    'TCamposExtrasEntidades', TJSONObject.Create([
      'F4B1', ''
    ]),
    'TPropostaItems', TJSONArray.Create([
      TJSONObject.Create([
        'Chave', '92EDC',
        'Ex', '0'
      ])
    ]),
    'TPropostaPagamentos', TJSONArray.Create([
      TJSONObject.Create([
        'Chave', '522',
        'Ex', '0'
      ])
    ])
  ]);
  Terminate;
end;

I would like to create a code that accesses JSON and changes the Asset value in the Tproposta item to '10'.

I’m using Free Pascal and Lazarus.