Abd al-Karim narrated that Sayyiduna Ali and Sayyiduna Ibn Mas'ud (may Allah be pleased with them both) said concerning a slave girl who is forced: "If she was a virgin, the compensation is one tenth of her price, and if she was previously married, it is one twentieth of her price."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9662