The black cow and the white cow.

A man goes hiking and he sees a farmer with two cows, one is black and the other is white. The man walks up to the farmer and asks him "What do you feed the cows?" The farmer asks "The black one or the white one?".
"The black one" says the man.
"I feed it grass."
"What about the white one then?"
"I feed it grass too."
The man nods "And where do the usually sleep?"
"The black one or the white one?" the farmer asks.
"The black one"
"In the barn"
"What about the white one?"
"It sleeps in the barn too." Says the farmer.
The hiker starts getting frustrated, "And what do you use them for?" he asks.
The farmer asks again "The black one or the white one?".
"The black one"
"Well I use it to get milk"
"And the white one?"
"I use it to get milk too."
The hiker gets extremely angry, and yells "What the hell is wrong with you? You keep asking me which cow I mean, then give me the same response for both!"
The farmer answers calmly "Well because the black cow is mine."
"Oh, and what about the white one?"
"It's mine too.."