Question 1    [10 points]

You are looking for a hotel to stay at for an upcoming Operations Management conference in San Francisco. You have narrowed the candidates down to four hotels with the following rates and satisfaction ratings.

Identify all hotels that are dominated by another hotel, and which hotel(s) dominate them?

Question 2    [30 points]

(a)  [10 points] A Wegmans store sells 640 boxed of Kellogs Corn Flakes per week. The average inventory

of Kellogs Corn Flakes is 3680 boxes. How long does a box spend in the store on average?

(b) [10 points] Boeing currently has a backlog of 4,648 undelivered planes of various sub-types of its very popular B737 model. Last year, Boeing delivered a total of 529 planes to customers. Use this data to estimate how long on average customers have to wait for a new plane to be delivered?

(c) [10 points] On average, a hospital sends out bills for $14,300,000 per week for patient care. It takes 105 days on average before they get paid. How much money do the responsible parties owe the hospital on average? Note: use 1 week = 7 days.

Question 3    [25 points]

Consider the following three-step process used in a custom dressmaker shop.

Each step has a single specialized employee assigned. Assume that the process operates 8 hours per day, and that demand exceeds capacity.

Question 4    [30 points]

An injection molding machine is used to make plastic tubes for syringes. The dimensions of the tubes need to be controlled very carefully to make sure that the correct dosage is given, hence the machine needs to be reset and recalibrated after every 600 tubes produced.  The recalibration process takes 40 minutes.  When running, the machine can produce one tube every 14 seconds, and in the long run, the injection molding machine can exactly keep up with demand.

(a)  [10 points] What is the injection molding machine’s capacity for producing tubes for the given batch size?

(b) [10 points] What is the utilization of the injection molding machine?

(c) [10 points] What is the maximum inventory of tubes (assume tubes are used at a constant rate)?

Question 5    [25 points]

A smoothie stand at the Lilac Festival sells two types of smoothies: fruit smoothies and vegetable smoothies. The smoothies are made by two workers. One measures the ingredients, and the other operates the blender, pours out the smoothie into a disposable cup and rinses the container in preparation for the next smoothie. Finally, a third worker takes the order and collects payment from the customer.  The processing times (in seconds) per smoothie are as follows.

Historically, 58% of the orders are for fruit smoothies and the rest for vegetable smoothies.  During peak times, the stand expects 80 smoothie orders per hour.

(a)  [15 points] Find the implied utilizations for all three resources during peak demand times.

(b)  [10 points] Assuming the product mix is unchanged, what is the capacity  (in smoothies/hr) of the

smoothie stand?

Question 6    [10 points]

You are planning a trip to Hong Kong for Spring Break, and have collected the information below on four flights (A, B, C and D). Of course being a student, the lower the fare, the better, and (like presumably most people) you prefer shorter flights over longer ones. Identify all the flights that are dominated by other flights and which flight dominate them and enter your answer in the bottom row of the table.  Enter “none” if a flight is not dominated by any of the other flights.

Question 7    [30 points]

(a) [10 points] NorthEast Airlines is a low-cost, no-frills airline.  NorthEast operates 113 flights/day, and the average flight takes 86 minutes.  How many flights does NorthEast have in the air on average? [Assume 1 day = 24 hours.]

(b) [10 points] A library has 42,000 books in its collection, and lends out 15,132 books/year. On average, 903 books are out with customers at any given time. How many weeks do customers keep a borrowed book on average? [Assume 1 year = 52 weeks.]

(c) [10 points] A fully automated, machine-paced smart watch assembly line has a cycle time of 35 seconds and at any given time there are 78 watches on the line. How many minutes does each watch spend on the line being assembled?

Question 8    [40 points]

Spectrum Electronics produces high quality OLED panels for use in mission critical applications (aircraft cockpits, air traffic control, marine control, etc.).  Production processes for OLED panels are complicated and consist of many steps, but for our purposes, we will simplify the process into three major stages. Since the process is technologically still in its infancy, yields are fairly low.  Information about process yield and capacity are given in the table below.

The yield percentage listed gives the percentage of panels that pass quality control performed after each step. Panels that fail to pass quality control are discarded immediately and do not go to the next step.

(a)  [10 points] Draw a process flow diagram for this process.

(b) [5 points] What is the overall yield (= nr of good panels produced / nr of panels going in) for the process?

(c) [10 points] Suppose that 180 panels per day are started into the process. Find the implied utilization for each step.

(d) [5 points] What is the bottleneck in the process?

(e) [10 points] What is the capacity of the process (in good panels produced per day)? 

Question 9    [40 points]

A car detailing shop uses a four step process, with the following steps and processing times..

Step:             Exterior Wash    Exterior Wax    Interior Clean    Interior Shine Processing time:       32 minutes         39 minutes        28 minutes        41 minutes

Each step is staffed with a single worker, who costs $22.80/hour, including wages and benefits.