The Project incomes, the beginning of the period, and the end of the period values ($ 000) are in the following table. WACC (discount rate) is 10% and the alternative return is 15%. Compute the cash flow and determine the optimum renewal period.

Periods	Project incomes En	Value at the beginning of the period R(n-1)	end of the period Rn
1 1	1,200	2,400	2,100
222 2	1,530	2,100	1,800
3 3	840	1,800	1,200
4 4	660	1,200	600
5 5	420	600	0