It would cost $6 billion to keep the federal Stafford loans for college kids at at subsidized rate of 3.4 percent. And that’s for just one year. Without action by Congress, new Stafford loan interest rates will double this summer. Nobody, including U.S. Rep. Joe Courtney, who is leading the fight to preserve the low rates, has a plan for coming up with that $6 billion yet. A good question for House and Senate candidates — how would you vote on a plan to extend the Stafford loan’s below-market interest rates?