Currently, State University can store 200 files on hard disk, 100 files in computer memory, and 300 files on tape. Users want to store 300 word-processing files, 100 packaged-program files, and 100 data files. Each month a typical word-processing file is accessed eight times; a typical packaged-program file, four times; and a typical data file, two times. When a file is accessed, the time it takes for the file to be retrieved depends on the type of file and on the storage medium (see Table below). If the goal is to minimize the total time per month that users spend accessing their files, formulate and solve a model that can be used to determine where files should be stored.

Storage Medium Hard disk Memory Tape Word Processing 5 2 10 Time (Minutes) Packaged Program 4 1 8 Data 4 1 6