FED'S JEFFERSON SAYS THERE IS 'GREAT WISDOM IN THE FED'S DUAL MANDATE' AND THAT THE FED IS FIRMLY COMMITTED TO RETURNING INFLATION TO 2% IN A TIMELY MANNER, HAVING TO BE PREPARED TO DO THE NEEDED WORK TO VALIDATE INFLATION EXPECTATIONS, WHICH HE SAYS SHOW THE FED IS CREDIBLE ON GETTING INFLATION DOWN AFTER A 'CASCADE OF SHOCKS'.