Select from the drop-down menus to correctly complete the proof. To prove that 4π is irrational, assume the product is rational and set it equal to ab, where b is not equal to 0: 4π=ab. Isolating π gives π=a4b. The right side of the equation is Choose... . Because the left side of the equation is Choose... , this is a contradiction. Therefore, the assumption is wrong, and the number 4πis Choose... .