Reconsider the example used to illustrate the deterministic periodic-review model in Sec. 19.4. Suppose that the following single change is made in the example. The cost of producing each airplane now varies from period to period. In particular, in addition to the setup cost of $2 million, the cost of producing airplanes in either period 1 or period 3 is $1.4 million per airplane, whereas it is only $1 million per airplane in either period 2 or period 4. Use dynamic programming to determine how many airplanes (if any) should be produced in each of the four periods to minimize the total cost.