Suppose you take out a 30-year, $100,000 mortgage at 6%. After 10 years, interest rates go down to 4%, so you decide to refinance the remainder of the loan by taking out a new 20-year mortgage. If the...

Suppose you take out a 30-year, $100,000 mortgage at 6%. After 10 years, interest rates go down to 4%, so you decide to refinance the remainder of the loan by taking out a new 20-year mortgage. If the cost of refinancing is 3 points (3% of the new mortgage amount), what are the new payments? What threshold interest rate would make refinancing fiscally unwise? (Assume that the points are rolled in with the new mortgage.)