Exchange at Walmart

I'm at the pharmacy counter, being all but fingerprinted in the process of buying pseudoephedrine hydrochloride (sudafed). We get to the part where I have to sign a contract on a computer screen, and the pharmacist says, "When you sign that, you're just saying you won't start a meth lab in your basement." I said, "If I knew how to build a meth lab, I'd be in an entirely different field." She said, "Oh. You must be at the law school."