We let tal be the effective interest rate of the investment fund, where t < . Using the definition of effective interest rate and the accumulation function of the investment fund, show that for any 0t < to $1 is invested at time t, and no additional deposit/withdrawal are made within (t, tel. To find (13) for this case, you need to reduce the problem into the cases when there is only a single deposit made at the beginning of the period. Think about the result derived in (a) with suitable choice of to.)