That's the certificateless, sick, old man speaking

Yes, Buhari can do that. If Nigeria stops selling our crude oil, then supply of crude in the international market will reduce and price will increase. Junior Secondary School Business Studies should tell you this. Imagine if Nigeria, Russia and Venezuela stops selling crude oil, don't you think that there will be huge shortage of supply at the international market? Definitely, price will go beyond $500 per barrel.

Use your brain and stop stalking Buhari.