Please plug into excel too

Case Problem

Metropolitan Police Patrol

The Metropolitan Police Department was recently criticized in the local media for not responding to police calls in the downtown area rapidly enough. In several recent cases, alarms had

sounded for break$-$ins, but by the time the police car arrived, the perpetrators had left, and in one instance a store owner had been shot. Sergeant Joe Davis was assigned by the chief

as head of a task force to find a way to determine the optimal patrol area $($dimensions$)$ for their cars that would minimize the average time it took to respond to a call in the downtown

area.

Sergeant Davis solicited help from Angela Maris, an analyst in the operations area for the police department. Together they began to work through the problem.

Joe noted to Angela that normal patrol sectors are laid out in rectangles, with each rectangle including a number of city blocks. For illustrative purposes he defined the dimensions of the

sector as x in the horizontal direction and as y in the vertical direction. He explained to Angela that cars traveled in straight lines either horizontally or vertically and turned at right angles.

Travel in a horizontal direction must be accompanied by travel in a vertical direction, and the total distance traveled is the sum of the horizontal and vertical segments. He further noted

that past research on police patrolling in urban areas had shown that the average distance traveled by a patrol car responding to a call in either direction was one$-$third of the dimensions

of the sector, or x$//3$ and y$//3.$ He also explained that the travel time it took to respond to a call $($assuming that a car left immediately on receiving the call$)$ is simply the average distance

traveled divided by the average travel speed.

Angela told Joe that now that she understood how average travel time to a call was determined, she could see that it was closely related to the size of the patrol area. She asked Joe if

there were any restrictions on the size of the area sectors that cars patrolled. He responded that for their city, the department believed that the perimeter of a patrol sector should not be

less than $5$ miles or exceed $12$ miles. He noted several policy issues and staffing constraints that required these specifications. Angela wanted to know if any additional restrictions

existed, and Joe indicated that the distance in the vertical direction must be at least $50\%$ more than the horizontal distance for the sector. He explained that laying out sectors in that

manner meant that the patrol areas would have a greater tendency to overlap different residential, income, and retail areas than if they ran the other way. He said that these areas were

layered from north to south in the city, so if a sector area was laid out east to west, all of it would tend to be in one demographic layer.

Angela indicated that she had almost enough information to develop a model, except that she also needed to know the average travel speed the patrol cars could travel. Joe told her that

cars moving vertically traveled an average of $15$ miles per hour, whereas cars traveled horizontally an average of $20$ miles per hour. He said that the difference was due to different traffic

flows.

Develop a linear programming model for this problem, and solve it by using the graphical method.