What would happen if a Black Hole and White Hole Collided? Given our understanding of both black holes and white holes, what would be the outcome if they were both to suddenly collide?

Black Holes:


  A black hole is a region of spacetime from which gravity prevents
  anything, including light, from escaping. The theory of general
  relativity predicts that a sufficiently compact mass will deform
  spacetime to form a black hole. The boundary of the region from which
  no escape is possible is called the event horizon.


White Holes:


  In general relativity, a white hole is a hypothetical region of
  spacetime which cannot be entered from the outside, although matter
  and light can escape from it.
From Wikipedia: 


  In quantum mechanics, the black hole emits Hawking radiation and so can come to thermal equilibrium with a gas of radiation. Because a thermal-equilibrium state is time-reversal-invariant, Stephen Hawking argued that the time reverse of a black hole in thermal equilibrium is again a black hole in thermal equilibrium. This implies that black holes and white holes are the same object


The excerpt above was an argument made by Stephen Hawking, explaining that a white hole and a black hole are essentially the same object. With this in mind, we can assume that the collision will be between two black holes. The result will then be the radius of the black hole added to the radius of the white hole.