Iran's parliament speaker Mohammad Bagher Ghalibaf has taken a swing at Donald Trump, and he brought an economics formula along. Invoking the Taylor equation, the rule central banks use to set interest rates, he suggested US monetary policy is straining while global oil prices climb and inflation keeps biting. The jab turns dry macroeconomics into a talking point about who is really paying for Washington's pressure campaign. Whether Iran can move American rates at all is doubtful, but the mockery lands on the cost side of the ledger.