Given : A fund that starts with a zero balance with time zero. Fund accumulates with a varying force of interest. The formula for the function is given: A $100,000 is deposited at time 2. To find: No. of years from the time of deposit for the fund to double. Solution :In case of a fixed rate of interest, it gradually decreases in relation to its value as time increases. The interest on interest is also accumulated. With the given function, t>0 and deposit is made at time 2. i.e when t=1. Substitute the value of t in the function, we get, Del(t)= 2*(1)/((1^2 + 1) =1 No of years for fund to double is 1 year..