OYO Tech Lead/Entry Level Manager interview questions

Rain water harvesting System design an app like oyo. One intersting thing was, User with app can invite 10 ppl. S/he will get reward for inviting if other party does booking via Oyo. But invitation has to be intelligent. Like, user has only 10 invites. How can I suggest (from app) that, invite these 10 ppl which are more likely to do booking with oyo. App has only access to user's contact. No access to location, no fb friend list, no fb photos etc etc.