If I play with PC or with partner not enough mutual experience, I would reply 3nt safe bid. You don't have majors and a lot of points it would mean like 15. If 1c was not full hand opener, they pass. If opener had actually 15+ they should reply 4nt a slam invite. On which we reply of course 6nt. In the end it is either 3nt, 6c or 6nt.