Bonus Problem 1 (Optional, 20 marks) *Note: In this problem, you are going to explore some techniques in evaluating effective interest rate in an investment fund. We let a(t) (where t > 0) be accumulation function of an investment fund launched at time 0. Questions (a) We let i[t,tz] be the effective interest rate of the investment fund, where t 0) be accumulation function of an investment fund launched at time 0. Questions (a) We let i[t,tz] be the effective interest rate of the investment fund, where t