Proprietor sale his used Car

proprietor purchase car his firm name when gst not introduced. Now he wants to sale his car to car dealer. This car is fixed asset in his books of accounts. supose Books value 200000 and sale value 300000. My question how can I prepare invoice. GST is applicable or not. If applicable how can calculate gst and what is rate. I know ITC not claimed by me. If gst applicable I can show it gstr1 or not. kindly clarify briefly any experts .