How do I find out the bhp of my daughter's imported Yamaha TZR50?

Hi all. My husband and I recently bought our 16 year old daughter a 1995 Yamaha TZR50R imported from Japan. We have finally received the DVLA registration form and it asks for the bike's bhp. Does anyone know where we can find this information? We think that there are no other TZR50R's in Britain so we hope that someone from Europe or beyond can help to answer this question.

Please can I have only sensible answers as this is the hopes of a young woman desperate to get on the road.