Problem:

A person has 3 units of money available for investment in a business opportunity that matures in 1 year. The opportunity is risky in that the return is either double or nothing. Based on past performance, the likelihood of doubling one's money is 0.6, while the chance of losing an investment is 0.4. Money earned one year can be reinvested in a later year and investments are restricted to unit amounts.

When dynamic programming is used to find the investment strategy for the next 4 years that will maximize the expected total holdings at the end of that period, the problem is formulated as a four-stage process with each stage representing a year. The states sj are the amounts of money available for investment for stage j (j = 1; 2; 3; 4).

Let f_j(s_j) denote the maximum expected holdings at the end of the process, starting in state sj at stage j.

(a) By clearly explaining your reasoning show that a recursive formula for finding the maximum expected holdings at the end of four years is given by

for j = 1; 2; 3 and 4, where the values of α and β are to be determined.

(b) Write down an expression for f₅(s).

(c) Find the maximum expected holdings at the end of the four years.