This is in the collections, The Complete Robot and Robot Visions.
Daneel is passing near Earth when the spaceship he is on has a legal issue with two passengers, so he stops in at Elijah’s office to get some help resolving the situation.
Admittedly, you already know which mathematician is lying long before the big reveal, but you read it anyway just coz you want to see how Elijah comes to the same conclusion.
All in all, a nice little novella to bridge the gap between The Naked Sun and The Robots of Dawn.
