elephant = { Clyde, Dumbo, Tuffi}
keeper = { Fred, Hank}

likes(elephant,keeper)

 2.1972 likes(x,y) // 2.1972 = ln(0.9/0.1)
-0.8573 likes(x, Fred) // -0.8573 = ln(0.3/0.7)
likes(Clyde, Fred). // hard formula