A scientist works on a new drug that he feels will enhance one's mental capacity.   It took years to develop and combine the right elements.   As time went on, he learned a way that he could mix it with H2O for ease.   But the FDA wouldn't give him permission to sell his drug without a trial.  So he set out. He found an old prostitute willing to try the drug.   She was already having trouble remembering how much to charge.   What could it hurt.   Arrangements were made and she was brought to the laboratory and there the drug was mixed with some H2O and provided. After a spell, her memory was tested.   And it was found that there was no improvement. what is a pun that goes with this story?