$$200,000$ mortgage is amortized over $25$ years with monthly payments at an interest

rate of $6\%$ compounded semi$-$annually. Suppose you made a single lump sum payment of $$6000$

at the end of the second year of the mortgage. $).$ How long would it now take to pay off the

mortgage $($calculate the number of years$)?$ How much interest is paid over the life of the mortgage