The force of interest

  (Problem 11.2) Find the accumulated value of 1 at the end of n years if the force of interest is δt = 1/1+t. (Problem 11.9) Jennifer deposits 1000 into a bank account. The bank credits interest at a nominal annual rate of i compounded semi-annually for the first 7 years and a nominal annual rate of 2i convertible quarterly for all years thereafter. The accumulated amount in the account after 5 years is X. The accumulated amount in the account at the end of 10.5 years is 1,980. Calculate X.