Einstein agreed with Hans, so they changed places.
At the university, Hans was guided to a platform, where he stood surrounded by professors and students.
Einstein took a seat in the audience, listened to Hans give his lecture perfectly, and joined in the applause at the end.
However, before Hans left the platform, a professor shouted from the audience, 'I'd like to ask you a difficult question.'
He then asked a question so complex that Hans had no idea what he was talking about.
Einstein thought, "Oh no! Now we're in trouble.'
But Hans just laughed and said, "That's not a difficult question.
In fact, it's so easy that even my driver knows how to answer it. Hans, please...'
Einstein stood up and answered the question perfectly.
They left the university, with Einstein driving.
A little later, Hans offered to drive.
'No, my friend,' laughed Einstein. 'It's a pleasure to drive a genius like you, Hans.'