After two years of the first five-year term at 6.7% compounded semiannually, Dan and Laurel decide to take advantage of the privilege of increasing the payments on their $210,000 mortgage loan by 10%. The monthly payments were originally calculated for a 25-year amortization. 

a. How much will the amortization period be shortened?

b. What will be the principal balance at the end of the five-year term?