Katherine invested $$1,900$ at the beginning of every $6$ months in an RRSP for $11$ years. For the first $4$ years it earned interest at a rate of $4\mathrm{.}80\%$ compounded semi$-$annually and for the next $7$ years it earned interest at a rate of $5\mathrm{.}20\%$ compounded semi$-$annually. question one: Calculate the accumulated value of his investment after the first $4$ years. question two: Calculate the accumulated value of his investment at the end of $11$ years. question three: Calculate the amount of interest earned from the investment.