A Soviet engineer needs some plumbing done in his apartment, and calls for a plumber. The plumber arrives, does his thing, and hands over the bill. The engineer is shocked. -'What, this is like a quarter of what I make in a month - for half an hour's work???'
Plumber shrugs. -'Well, why don't you come join us? Easy work, well paid, no responsibility - just remember to keep mum about your degree, as we're not supposed to hire academics.'
Our engineer contemplates this for a while, applies for a job as a plumber - and gets it.
All is well, good money, no responsibilites - until management requires that they take evening school classes to gain new skills and thus better build socialism. So, grudgingly, our engineer enrolls in a math class and, upon arriving, finds that the teacher wants to establish what the plumbers already know.
-'You over there - could you please come to the blackboard and show us the formula for the area of a circle?' he asks our engineer.
Standing at the blackboard, he suddenly realizes he can't for the life of him remember the formula; while a bit rusty, he soon figures out how to reason it out - furiously writing out integrals on the blackboard, only to find the area of a circle is -(pi)*r^2.
Minus? How did a negative enter into it, he thinks, going over his calculations once again. No, still gets the same result. Sweat building, he turns away from the blackboard for a moment, turning to the other plumbers watching.
As in one voice, they all whisper -'Comrade, you must switch the limits to the integral!'
