how to display Qmessagebox in the middle of the device?

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QT-Creator

Hi,
i m tried with Qmessagebox in my application to show some data and image in the middle of the device . but i m able to display text in my scren bt not in the middle.
m

QMessageBox noc;
QString er=tr("When you want to start reading the holy book :\nAllah has asked us to begin the search for refuge against Satan the stoned. Indeed, Allah says in his noble book,\nSo when you want to recite the Qur’ân,seek refuge with Allah from Shaitân (Satan), the outcast (the cursed one)...»Surah An-Nahl verse 98. \n This verse encourages the reader to begin each recitation by the formula :?? ??????? ?????? which is the key to divine protection.\nOn the other hand, at the beginning of each surah (Surah At-Except tawbah - The Repentance), we find what is called in Arabic al-Bismillah which is the formula: ??? ???? ?????? ?????? and which means In the name of God, the Most Gracious, the Most Merciful.");
  noc.setText(er);
  noc.exec();

please suggest me how to show in the middle of the screen . My screen size is 360*640.

Regards,
Arpita