Witch "Tintin" book will be the second movie?

    The Tintin movie that is coming out in Wednesday is based on the comic series by Herge. Will you might think that the movie coming out is based on the first book of the series, will actually Secrets of the Unicorn is the eleventh book of the series. So now what will be the second movie based on?
    Its rumored that the second will be based on Prisoners of the Sun. But now producer Kathleen Kennedy says the truth-

    ‘Prisoners of the Sun’ was a very, very early discussion, and it isn’t under discussion anymore. We’ve still got Anthony Horowitz working on the second movie, and we don’t know what we’re doing with the third movie yet.

        So now what we’re thinking [for the second film] is what new characters do we want to introduce? Well, we’ll probably introduce Calculus and bring him into the fold.

     So this probably means that its gonna be based on The Calculus Affair. Then she says that its a bit tricky for Peter Jackson since hes directing both the new Tintin and the second Hobbit-

          It’s tricky getting everybody but that’s how we did the first movie, sort of passing the baton. When Steven was available, he’d jump in, and when he was busy, Peter would pick up the slack. It was kind of amazing how they’d work together. We never knew how this would work, but it worked out really, really well.

       Well there it is, witch could it be, Prisoners of the Sun or The Calculus Affair?