Determine the optimal design return period from a flood control project with damage and capital costs as given in Table 13. 16.

TABLE 13.16 Return Period, Damage Cost, and Capital Cost in Problem 13 T (Return period) 1 2 5 10 15 Damage cost ($x10) 0 40 120 280 354 Capital cost ($/year x10) 0 6 28 46 50 58 20 25 426 500 600 54 58 50 100 200 800 1.000 80 120 160