Mortgage refinancing activity has surged in recent days as homebuyers rush to take advantage of suddenly plummeting loan rates. The frenzy to find a new loan began when mortgage rates suddenly dropped in the wake of the Federal Reserve’s Nov. 25 announcement that it will buy up to $500 billion of securitized loans. The rate drop helped fuel a whopping 203.3 percent increase in refinancing activity for the week ending Nov. 28, according to the Mortgage Bankers Association.