Fed's Hammack Says Do Not Take Anchored Inflation Expectations For Granted, With Businesses Planning Price Increases Beyond Any Rise In Input Costs A Sign Of Inflationary Mindset Taking Hold; Fed Officials Have A Responsibility To Explain Their Decisions; It Is Important To Spell Out Reaction Function So Businesses And Households Can Plan Effectively; If The Public Understands Where The Fed Is Heading, It Can Limit Market Volatility, Avoid Mistakes; A Reaction Function Is Not The Same As Committed Forward