Variance Associates (VA) is a commercial aircraft leasing firm. It has two customers, FearUs and Oops, both of which are major overnight package delivery companies. Airlines and overnight package companies normally own only a portion of their total fleet of aircraft, and lease the balance on an as-needed basis. FearUs and Oops have long-term contracts with Variance, under which they have the option to request planes from VA on a monthly basis. Specifically, each month FearUs can request up to 4 planes for the succeeding month, at a price of $150,000 per month for each plane requested. Oops can also request up to 4 planes for the succeeding month, at a price of $150,000/plane per month.
Variance owns 8 planes, in order to cover its contracts. It has had both good and bad years in the past, but cumulatively it is just breaking even. Out of frustration, the president of Variance Associates hires a consultant.
McBain & Co. assigns Poindexter Harbus (Fecbus ’18) to assess the problem and deliver a solution. The president of VA explains to Poindexter that although VA has great margins on its leased planes, the firm’s total performance has been uneven. Poindexter learns that VA has fixed costs of $75,000/plane per month (i.e., whether or not the plane was leased that month), but that all other costs incurred when a plane is in service (e.g., fuel, maintenance, crews) are covered by the customer at the customer’s expense.
Poindexter begins his analysis by examining Variance’s data on the demand for planes by each customer. He computes relative frequencies and tabulates the following probabilities:
After appraising the situation, Poindexter reports to the president of Variance Associates:
In order to improve Variance’s profitability, Poindexter proposes a new, two-tier strategy for VA:
To determine expected profits under the new strategy, Poindexter needs to determine the probability that total demand would be 8 planes (i.e., a “stock out” event). To do this, Poindexter multiplies the probability distributions for each customer’s demand to construct a probability table:
Some of you schemers may happen on a clever strategy to defraud Variance here. To head you off at the pass, assume that Variance is sharp enough not to let FearUs know how many planes Oops has requested for the coming month, and vice versa, and that there is enough competition between FearUs and Oops that they’re not about to tell each other, either.
which he uses with the revenue, fixed cost, and compensation policy cost numbers to compute expected profits under the new strategy.
Question 2: Briefly explain how Poindexter derived the distribution for total demand. Specifically, why is P(total demand = 1) = .05? (Hint: Start from his 5 × 5 table)
Question 3: Under Poindexter’s new strategy, what does Poindexter’s analysis indicate VA’s expected profits will be?
The president of VA likes Poindexter’s results. But after pondering Poindexter’s reasoning for a few minutes, he wonders: “Why downsize by just one plane if we expect demand to be only four planes?” He reasons, “If that’s what we expect, we should just carry four planes. Instead of carrying enough planes to handle the maximum demand, we’ll carry enough to handle the average demand, and suitably compensate FearUs and Oops with a free plane if we’re short.”
Question 4: Will VA see higher expected profits with only 4 planes to meet customer demand? Why or why not? (Hint: Make another table.)
Question 5: Now that you have the results for the expected number of planes, what is the optimal number of planes for VA to own?
Variance Associates’ accountant, Flim Flambert, now joins the fray. Flim is concerned with the risk in VA’s monthly cash flow position under the old and new strategies. To get a measure of this risk, Flim computes the standard deviation in monthly income. He then points out a problem in Poindexter’s analysis, and announces “I can’t reconcile Poindexter’s probabilities with our past cash flows. We have more variability in our cash flows each month than Poindexter’s figures imply.”
Flim justifies his conclusion with the actual relative frequencies of historical monthly cash flow amounts for VA:
Question 8: What can we infer from the table about the demand patterns of the two customers?
Question 9: In their analyses, Poindexter and Flim used different probability tables for the joint distribution of FearUs’ and Oops’ demands. In doing so, they arrived at the same number for the expected value of total profit under the 8 plane policy. They did not arrive at the same number for the standard deviation of total profit, however. Why not?
With the new probability table, Flim and Poindexter re-analyze Poindexter’s original proposal to improve VA’s profitability. Specifically, using Flim’s new probability table they calculate the optimal number of planes for VA to carry, and the corresponding expected profit.
Question 10: What is the optimal number of planes to own, if VA compensates customers with
$150k/plane for shortages? What are VA’s expected profits under this strategy?