CS 177 Winter 2007Assignment 1

Service Department for Home Theatre SuperStore

Due: Wednesday, January 30, 11:59 PM

Introduction

"Big Buy" is a large retail chain, with dozens of home electronics stores throughout Southern California. One of their most profitable items is the sale of Home Theatre Systems (HTS). A typical HTS consists of a big-screen high definition television (HDTV), multichannel surround-sound system (amplifier and speakers), DVD player, TiVO, cable/satellite receiver, VCR, iPod, digital still camera (or its removable memory card), camcorder, some video game consoles and possibly a regular computer. Typically, each of these components comes with its own proprietary multifunction wireless remote control (featuring a unique user interface, of course!), and requires the user to correctly connect a huge rat's-nest of cables that carry: AC power; analog and/or digital audio and video streams; command functions, Internet connectivity, etc., to link it with the other components in the HTS.

For the most part, Big Buy customers are pretty clueless about how to set up and use their new HTS, so they usually purchase a one-year service contract with the "Firing Squad" (Big Buy's service department). In this case, the Firing Squad will take care of delivery and initial setup of the new HTS (and tell the customer which button to push to watch football or Oprah), and thereafter will provide a 24-hour telephone help-line, and (if necessary) schedule a diagnosis and repair visit to the customer's home at any time within the one-year contract period.

As manager of the Firing Squad, it is your job to keep these HTS customers happy while minimizing Big Buy's cost of providing that service.

Problem Specifications

You can configure your crew into two-person teams traveling in a large truck, or individuals driving a minivan. Assume that the one-way travel time to the next customer site (or back to headquarters) is uniformly distributed between 10 and 20 minutes for a large truck, and uniformly distributed between 5 and 15 minutes for a minivan. Also assume that the large truck can carry everything required for all jobs in their schedule, so the truck crew won't return to headquarters until the end of the four-hour block. However, the minivan only has limited space, and must return to headquarters after completing two delivery jobs (to pick up more stuff for the next customer) or picking up four pieces of equipment at on-site repair visits (to drop off customer equipment that requires major repair or replacement).

Assume that the work schedule for Firing Squad members is divided into four-hour blocks of time. Below is the normal set of jobs that your team must accomplish during a typical four-hour block.

• Delivery and initial setup for 10 new HTS customers. Since each customer purchases a different set of components, there is no way to change the set of jobs assigned to a particular crew or individual after they leave headquarters, even if someone falls behind while others are ahead of schedule.
• For a two-person crew, this job requires a uniform time between 10 and 20 minutes to unload and unpack all the boxes,  connect all the components, test the system, and demonstrate its use to the customer.
  
• For an individual, the same job requires a uniform time between 20 and 40 minutes to complete.

• On-site repair visits for 25 existing customers. With probability 0.5, the Firing Squad member(s)  can solve the problem during a single visit. Otherwise, they will need to take back some broken piece of equipment to the shop for major repair. (Delivery of the repaired or replacement component will be scheduled later, as a separate repair visit.) Since all Firing Squad members are equally qualified to carry out an on-site repair visit (and they did not pick up any customer-specific items when they left headquarters),  repair jobs can be dynamically reassigned from one crew/individual to another to balance their workload. This is particularly important for individuals with minivans, whose available space for picking up broken pieces of equipment fills up randomly.
• For a two-person crew, the diagnosis/repair time is uniformly distributed between 10 and 30 minutes. If a broken piece of equipment is found, it takes an additional 5 minutes to load it onto the truck.
• For an individual, the diagnosis/repair time is uniformly distributed between 15 and 45 minutes. If a broken piece of equipment is found, it takes an additional 10 minutes to load it into the minivan.

Write a simulation program to model operation of the Firing Squad during a four-hour scheduling block. To simplify the problem, assume that you cannot assign a mixture of two-person crews and individuals to a single type of job, i.e., all initial setup jobs must be handled entirely by two-person crews or by individuals -- no mixtures are allowed.

Use your program to estimate how many Firing Squad members are required to complete this normal set of jobs in a approximately four hours using two-person truck crews and/or individuals with minivans. If the overall cost to Big Buy of each two-person crew and its truck is twice as high as the overall cost of each individaul with a minivan, estimate the least cost strategy for running your department.