ちなみにこのプログラムに手を加えろという問題です

const
    filename='test.txt';
var
    sum:    double;
    fp:    TextFile;
    str:    string;
begin
    sum:=0;
    try
        AssignFile(fp, filename);
        Reset(fp);
        try
            while (not Eof(fp)) do
            begin
                Readln(fp, str);
                sum:=sum+StrToFloatDef(str, 0);
            end;
            writeln(FloatToStr(sum));
        finally
            CloseFile(fp);
        end;
    except
        on E: Exception do Writeln(E.Message);
    end;
end.