(CNN) - Leave it to one of the kings of late night comedy to press Republican presidential candidate Herman Cain on his "9-9-9" tax plan and offer up his own suggestion to the former pizza executive.
"You ought to get some sort of toll-free number," Letterman told Cain in an interview set to air Friday. "You dial 9-9-9, you get a free pizza."
Although the plan is "clever" and "fun," Letterman, host of CBS' "Late Show with David Letterman," told Cain: "You don't even know what it means."
Cain's response? "It works."
The candidate's tax plan, a pillar of his White House bid, proposes replacing the current tax system with a 9% corporate tax, 9% income tax and 9% national tax rate.
"Instead of a free pizza when you dial 9-9-9 you're going to be able to get a job, that's the whole point, OK?" Cain said. "I'm about creating jobs."
But Letterman countered that the economy may be "beyond solvability at this point," to which Cain jokingly responded, "Are you trying to talk me out of this? He's trying real hard to talk me out of this."